Process for making shrink film comprising rapidly-quenched semi-crystalline polyamide

ABSTRACT

As a first aspect, the present invention is directed to a process for making a heat-shrinkable annular film, comprising: (A) extruding an annular extrudate downward from an annular die; (B) quenching the annular extrudate by applying a quenching liquid to the annular extrudate; (C) reheating the extrudate to an orientation temperature of from 130° F. to 210° F., resulting in a reheated annular extrudate; and (D) orienting the reheated annular extrudate while the reheated annular extrudate is in the solid state, the orientation being carried out with a total orientation factor of at least 2, so that the resulting oriented, heat-shrinkable film has a total free shrink at 185° F. of at least 10 percent. The extrudate comprises at least one semi-crystalline polyamide selected from the group consisting of: (i) polyamide 6, (ii) polyamide 66, (iii) polyamide 6/66, and (iv) polyamide 6/12. The semi-crystalline polyamide makes up at least 5 volume percent of the annular extrudate. At least 50% of the quenching liquid cascades down the annular extrudate for a distance of at least 2 inches. The quenching liquid makes initial contact with the annular extrudate within 0.1 to 8 inches of the annular die.

FIELD OF THE INVENTION

The present invention relates generally to processes for making flexiblefilms, particularly to heat-shrinkable films suitable for packaging enduse.

BACKGROUND OF THE INVENTION

Historically, most commercially-available, heat-shrinkable,food-packaging films have been polyethylene-based. Polyethylene,particularly ethylene/alpha-olefin copolymers, are relativelyinexpensive, have relatively low melting points, are readilyheat-sealable, and are readily oriented in the solid state, i.e., at atemperature between the glass transition temperature of the polymer andthe melting point of the polymer. Such films can be provided with arelatively high total free shrink value at, for example, 85° C. (185°F.).

In the last few years, semi-crystalline polyamide-based shrink filmshave begun to compete against polyethylene-based shrink films for thepackaging of fresh meat products, even though polyamide is moreexpensive than polyolefin. One reason is that semi-crystallinepolyamide-based shrink films can provide higher impact strength per milthan polyethylene-based films. Unlike patchless bags made frompolyethylene-based films, patchless bags made from semi-crystallinepolyamide-based films can provide adequate protection for some abusivefood products, such as some bone-in meat products.

However, semi-crystalline polyamide-based shrink films are difficult toproduce because it is difficult to carry out the solid-state orientationof the semi-crystalline polyamide necessary to impart the desired degreeof low-temperature heat-shrinkability. Recently a turn-key productionline has been developed and offered for sale by Kuhne Anlagenbau GMBH.Kuhne Anlagenbau GMBH developed this production line concurrently withits development of, and for the manufacture of, a turn-keysemi-crystalline polyamide-based multilayer heat-shrinkable packagingfilm. This Kuhne turn-key production line includes an elaboratequenching means beneath the extrusion die. The quenching means employsvacuum around the exterior of the annular extrudate as it emerges fromthe die, while at the same time applying water to the extrudate shortlyafter it emerges from the die. The vacuum is employed so that theannular extrudate does not collapse upon itself before it solidifiesenough that it is fully quenched. The vacuum around the outside of theextrudate affects the quenching of the extrudate, because the vacuumdraws the applied quenching water from the surface of the extrudate.

SUMMARY OF THE INVENTION

While the extrudate is ultimately quenched by the water in the Kuhneprocess, it would be desirable to quench the extrudate more rapidly, asthis could produce an extrudate that is more readily orientable. Itwould also be desirable to simplify the quenching apparatus. It wouldalso be desirable to improve the reheating and solid state orientationso that the extrudate is more readily oriented in the solid state. Itwould also be desirable to obtain a film that is more readilyorientable.

A process has been discovered for making an annular heat shrinkable filmcontaining a relatively high proportion of a high melting polyamide. Theprocess enables a more rapid quenching of an annular extrudate by theapplication of a quenching liquid to extrudate, the quenching liquidcascading down the extrudate for a distance of at least 2 inches, withthe quenching liquid making initial contact with the extrudate within adistance of from 0.1 to 8 inches from the position at which theextrudate emerges from the annular die.

The extrudate is extruded through an annular die. The quenching liquidcan be applied to the inside surface of the annular extrudate, or to theoutside surface of the annular extrudate. If the quenching liquid isapplied to the outside of the annular extrudate, it is necessary toprovide a means for supporting the annular extrudate, to prevent theannular extrudate from collapsing upon itself. The means for supportingthe annular extrudate is provided inside of the annular extrudate. Themeans for supporting can be a slightly superatmospheric pressure insidethe extrudate, and/or a physical support positioned inside of theannular extrudate.

An air shoe positioned inside the annular extrudate is a preferred meansfor supporting the annular extrudate. The air shoe has an exteriorsurface relatively close to the annular extrudate. The air shoe emitsair from a plurality of relatively small holes over its exteriorsurface, providing a cushion of air that supports the inside surface ofthe extrudate while the outside surface of the extrudate is contactedby, and in contact with, the cooling liquid applied to and cascadingdown the exterior surface. In this manner, a relatively large quantityof liquid can cascade down the outside surface of the extrudate toproduce very rapid quenching of the extrudate, producing an extrudatethat is more readily oriented in the solid state. The air shoe can besupplied with cool air in order to assist in quenching the annularextrudate.

As a first aspect, the present invention is directed to a process formaking a heat-shrinkable annular film, comprising: (A) extruding anannular extrudate downward from an annular die; (B) quenching theannular extrudate by applying a quenching liquid to the annularextrudate; (C) reheating the extrudate to an orientation temperature offrom 130° F. to 210° F., resulting in a reheated annular extrudate; and(D) orienting the reheated annular extrudate while the reheated annularextrudate is in the solid state, the orientation being carried out witha total orientation factor of at least 2, so that an oriented,heat-shrinkable film is produced, the oriented film having a total freeshrink at 185° F. of at least 10 percent. The extrudate comprises atleast one semi-crystalline polyamide, the semi-crystalline polyamidecomprising at least one member selected from the group consisting of:(i) polyamide 6, (ii) polyamide 66, (iii) polyamide 6/66, and (iv)polyamide 6/12, with the semi-crystalline polyamide making up at least 5volume percent of the annular extrudate, based on total extrudatevolume. The quenching liquid absorbs heat from the annular extrudate asat least 50% of the quenching liquid cascades down the annular extrudatefor a distance of at least 2 inches. The quenching liquid makes initialcontact with the annular extrudate at a distance of from 0.1 to 8 inchesdownstream of a point at which the annular extrudate emerges from theannular die.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of a two-step process for producing a fullycoextruded, heat-shrinkable, film in accordance with the presentinvention.

FIG. 2A is a schematic of an enlarged upstream portion of the two-stepfull coextrusion process illustrated in FIG. 1.

FIG. 2B is a schematic of an enlarged downstream portion of the two-stepfull coextrusion process illustrated in FIG. 1.

FIG. 2C is a schematic of an enlarged alternative upstream portion ofthe two-step full coextrusion process illustrated in FIG. 2A.

FIG. 3 is a cross-sectional view of an air ring assembly for use in theprocess of making a film in accordance with the present invention.

FIG. 4 is a schematic of a one-step process for producing a fullycoextruded, heat-shrinkable film in accordance with the presentinvention.

FIG. 5 is a schematic of a two-step process for producing anextrusion-coated, heat-shrinkable, film in accordance with the presentinvention.

FIG. 6 is a schematic of an end-seal heat-shrinkable bag.

FIG. 7 is a longitudinal cross-sectional view of the end-seal bag ofFIG. 6.

FIG. 8 is a schematic of a side-seal heat-shrinkable bag.

FIG. 9 is a transverse cross-sectional view of the side-seal bag of FIG.8.

FIG. 10 is a graph illustrating the difference between the opticalproperties of the film in accordance with the present invention versusvarious commercial polyamide-based films.

DETAILED DESCRIPTION OF THE INVENTION

As used herein, the term “fluid” is inclusive of both compositions inthe liquid state and compositions in the gaseous state. The term“liquid” applies to a composition in the liquid state, and the term“gas” refers to a composition in the gaseous state.

As used herein, the term “film” is inclusive of plastic web, regardlessof whether it is film or sheet. The film can have a total thickness offrom 0.5 mil to 30 mils, from 1 mil to 15 mils, from 1 mil to 8 mils, orfrom 1.5 to 6 mils, or from 2 mils to 6 mils, or from 1 to 5 mils, orfrom 2 mils to 5 mils, or from 2 mils to 4 mils, or from 2 mils to 3.5mils, or from 1.5 mils to 4 mils, or from 1 mil to 1.5 mils, from 0.5mil to 1.5 mils, from 0.7 mil to 1.3 mils, from 0.8 mil to 1.2 mils, orfrom 0.9 mil to 1.1 mils. In contrast, the thickness of the annularextrudate can be from 5 mils to 70 mils, from 10 mils to 50 mils, orfrom 12 to 40 mils, or from 13 to 30 mils, or from 14 to 25 mils.

The film of the present invention can be produced as a fully coextrudedfilm, i.e., all layers of the film emerging from a single die at thesame time. Alternatively, the film can be produced using an extrusioncoating process in accordance with U.S. Pat. No. 4,278,738, to Brax etal, which is hereby incorporated, in its entirety, by reference thereto.

As used herein, the term “quenching” refers to cooling an annularextrudate to accelerate the freezing of the polymers making up theextrudate. The process quenches by applying a quenching liquid to theannular extrudate within a distance of from 0.1 to 8 inches downstreamof the point at which the annular extrudate emerges from the annulardie. The liquid can be applied to the exterior surface of the annularextrudate, and/or to the interior surface of the annular extrudate.Liquid applied to the interior surface of the annular extrudate servesto both quench the extrudate and support the annular extrudate againstits tendency to collapse inwardly. If liquid is applied only to theexterior surface of the annular extrudate, a means for supporting theannular extrudate must be employed to avoid collapse of the extrudate.

While the quenching liquid is applied to the annular extrudate within adistance of from 0.1 to 8 inches downstream of the point at which theannular extrudate emerges from the annular die, the quenching liquid canbe applied to the surface of the annular extrudate within a distance offrom 0.1 to 6 inches downstream of the annular die, or from 0.1 to 5inches, or from 0.1 to 4 inches, or from 0.2 to 3.5 inches, or from 0.3to 3 inches, or from 0.4 to 3 inches, or from 0.4 to 2.5 inches or from0.5 to 3 inches, or from 1 to 3.5 inches, or from 1 to 3 inches, or from1 to 2.5 inches, or from 1.5 to 3.5 inches, or from 1.5 to 2.5 inches.

While at least 50% of the applied quenching liquid cascades down theannular extrudate for a distance of at least 2 inches, at least 70% cancascade for a distance of at least 3 inches, or at least 80% can cascadefor a distance of at least 4 inches, or at least 90% can cascade for adistance of at least 5 inches, or at least 99% can cascade for adistance of at least 8 inches, or substantially 100 percent of theliquid can cascade for at least 12 inches, or substantially 100 percentof the liquid can cascade for at least 24 inches.

While the quenching liquid cascades down the extrudate for a distance ofat least 2 inches, it may cascade down the extrudate for a distance ofat least 3 inches, or at least 4 inches, or at least 8 inches, or atleast 12 inches or at least 24 inches. In all of the examples of theinvention described hereinbelow, substantially 100% of the watercascades down the extrudate from the point at which the water contactsthe extrudate, with the water cascading down the extrudate substantiallyall the way to the nip rollers that collapse the annular extrudate intoits lay-flat configuration. This distance is at least 24 inches.

If quenching liquid is applied to the interior surface of the annularextrudate, it can be supplied to the interior surface via a centralpassageway through the annular die, with the quenching liquid beingapplied to the inside surface, this quenching liquid cascading downwardinto a collection pool above the point at which the annular extrudateconverges into lay-flat configuration. The quenching liquid can be drawnout of the collection pool and up through a discharge or recirculationconduit passing through the central passageway through the annular die.

If the liquid on the inside of the annular extrudate more than offsetsthe tendency of the annular extrudate to collapse, supporting means canbe provided to the exterior surface of the annular extrudate. Suchsupporting means can be a fluid impinging on the exterior surface of theannular extrudate, which fluid can be liquid and or gas.

As used herein, the phrase “water ring” refers to a ring-shaped devicefor delivering a stream of liquid (preferably water) onto the exteriorsurface of an annular extrudate. The ring itself is hollow, i.e., has acavity therein. The water ring is supplied with a quenching fluid(preferably water) that passes into the cavity within the ring and thenout through a slot in the inside surface of the ring, with the annularstream of water flowing out of the ring and onto the exterior surface ofthe annular extrudate, for the purpose of quenching the extrudate. Thegap in the water ring, from which the water flow is emitted, can bewithin the range of from 0.02 to 0.5 inch, or 0.03 to 0.3 inch, or 0.05inch to 0.25 inch, or from 0.07 inch to 0.16 inch. The water ring canemit quenching water at a temperature of from 0° C. to 25° C., or from5° C. to 16° C. More than one water ring can be employed in the process.More than one water ring can apply the water to the outside surface ofthe annular extrudate.

The means for supporting the annular extrudate immediately after itemerges from the die can be a fluid supplied to the interior volumewithin the annular extrudate (i.e., a gas or liquid supplied to thevolume between the point at which the annular extrudate emerges from theannular die and the point at which the annular extrudate converges intolay-flat configuration). The fluid is provided so that at least someportion of this interior volume has a pressure above ambient pressure.The pressure can be supplied by simple pressurization of the volume witha gas, or through the use of a stream of liquid emitted radially outwardfrom one or more sprayers or conduits or fluid flow emission members, orwith an air shoe.

As used herein, the phrase “air shoe” refers to a device to bepositioned inside an annular extrudate to support the extrudate as itemerges immediately after it emerges from the annular die, i.e., beforethe annular extrudate is quenched. The air shoe can have any desiredlength, or a length of from 4 to 50 inches, or 6 to 20 inches. The airshoe can have any desired diameter, or a diameter of from about 1 to 50inches, or from 2 to 25 inches, or from 4 to 12 inches. The air shoe hasa round cross-section and has an interior chamber supplied withpressurized air, with the pressurized air passing from the chamberthrough a plurality of small air passageway holes through the chamberwall. The air passageway holes can have any desired diameter, or adiameter of from about 0.01 inch to about 0.25 inch, or from 0.02 inchto about 0.1 inch. The air passageway holes can be spaced at uniformintervals over the surface of the air shoe. Each interior hole in thematrix of air passageway holes can have the same number of holesequidistant therefrom, such as 3 holes, four holes, 5 holes, 6 holes, 7holes, 8 holes, or 9 holes. The equidistant spacings can be any desireddistance, or can be from 2 to 40 millimeters, or from 4 to 20millimeters, or from 10 to 20 millimeters. The air shoe can be suppliedwith air under a pressure of from 1 to 100 psi, or from 5 to 90 psi, orfrom 10 to 80 psi, or from 40 to 100 psi, or from 60 to 90 psi. The airshoe can emit air at any desired temperature, or the air shoe can emitair at a temperature of from −10° C. to 25° C., or from 0° C. to 25° C.,or from 5° C. to 10° C.

Generally the air shoe has an outside diameter which is relatively closeto the diameter of the extrudate, so that the air emitted from the airpassageway holes in the air shoe provides an air cushion supporting theannular extrudate. The ration of the inside diameter of the annular diegap (from which the annular extrudate emerges), to the outside diameterof the air shoe, can be from 1:1.1 to about 1:0.5, or from about 1:1 toabout 1:0.8, or from 1:1 to 0.85; or from 1:0.99 to 1:0.90, or from1:0.98 to 1:0.92.

As used herein, the term “adhered” is inclusive of films which aredirectly adhered to one another using a heat seal or other means, aswell as films which are adhered to one another using an adhesive whichis between the two films. This term is also inclusive of layers of amultilayer film, which layers are of course adhered to one anotherwithout an adhesive therebetween. The various layers of a multilayerfilm can be “directly adhered” to one another (i.e., no layerstherebetween) or “indirectly adhered” to one another (i.e., one or morelayers therebetween).

As used herein, the phrases “seal layer,” “sealing layer,” “heat seallayer,” and “sealant layer,” refer to an outer film layer, or layers,involved in heat sealing the film to itself, another film layer of thesame or another film, and/or another article which is not a film. Heatsealing can be performed in any one or more of a wide variety ofmanners, such as melt-bead sealing, thermal sealing, impulse sealing,ultrasonic sealing, hot air sealing, hot wire sealing, infraredradiation sealing, ultraviolet radiation sealing, electron beam sealing,etc.). A heat seal is usually a relatively narrow seal (e.g., 0.02 inchto 1 inch wide) across a film. One particular heat sealing means is aheat seal made using an impulse sealer, which uses a combination of heatand pressure to form the seal, with the heating means providing a briefpulse of heat while pressure is being applied to the film by a seal baror seal wire, followed by rapid cooling.

In the multilayer, heat-shrinkable film of the invention, the seal layercan comprise a polyolefin having a density of from 0.88 g/cc to 0.917g/cc, or from 0.90 g/cc to 0.917 g/cc. The polyolefin can be an ionomeror an ethylene/alpha-olefin copolymer. In one embodiment, the seal layercan comprise at least one member selected from the group consisting ofvery low density polyethylene and homogeneous ethylene/alpha-olefincopolymer. The very low density polyethylene can have a density of from0.900 to 0.917 g/cm³, and the homogeneous ethylene/alpha-olefincopolymer can have a density of from 0.880 g/cm³ to 0.910 g/cm³.

A combination of low haze and high clarity have been obtained using aseal layer of 100% ethylene/alpha-olefin copolymer having a density of0.915 g/cm³. Metallocene catalyzed sealants with densities of 0.917g/cm³ or less, as well as very low density polyethylene having a densityof 0.912 g/cm³, can provide the film with a combination of low haze andhigh clarity. Plastomer type metallocene sealants with densities lessthan 0.910 g/cm³also provided low haze and high clarity.

As used herein, the term “barrier”, and the phrase “barrier layer”, asapplied to films and/or film layers, are used with reference to theability of a film or film layer to serve as a barrier to one or moregases. In the packaging art, oxygen (i.e., gaseous O₂) barrier layershave included, for example, hydrolyzed ethylene/vinyl acetate copolymer(designated by the abbreviations “EVOH” and “HEVA”, and also referred toas “ethylene/vinyl alcohol copolymer”), polyvinylidene chloride,amorphous polyamide, polyamide MXD6, polyester, polyacrylonitrile, etc.,as known to those of skill in the art. In addition to the first andsecond layers, the heat-shrinkable film may further comprise at leastone barrier layer.

The film may optionally have one or more barrier layers comprising ananocomposite, to enhance the barrier property or other properties ofthe film. The term “nanocomposite” refers to a mixture that includes amonomer, polymer, oligomer, or copolymer having dispersed therein aplurality of individual platelets obtained from an exfoliated modifiedclay. A modified clay is a clay that has undergone intercalation, whichis the process of forming an intercalate. An intercalant is, forexample, an ammonium ion that is absorbed between platelets of thelayered material (i.e., the clay particles) and complexed with the Na⁺cations on the plate surfaces. The intercalate is the platelets havingthe intercalant therebetween. Polymers suitable for use in thenanocomposites include low density polyethylene, linear low densitypolyethylene, medium density polyethylene, high density polyethylene,polypropylene, polyamide, polyester, and polyacrylonitrile. Otherpolymers suitable for use in the nanocomposites include ethylene vinylalcohol copolymer, ethylene vinyl acetate copolymer, polyvinylidenechloride, aliphatic polyketone, liquid crystalline polymers, epoxy, andpolyurethane adhesive. The use of nanocomposites to enhance barrierand/or other properties is disclosed in U.S. Pat. No. 6,447,860, toMueller et al, which is hereby incorporated, in its entirety, byreference thereto.

As used herein, the phrase “tie layer” refers to any internal layerhaving the primary purpose of adhering two layers to one another. Tielayers can comprise any polymer having a polar group grafted thereon.Such polymers adhere to both nonpolar polymers such as polyolefin, aswell as polar polymers such as polyamide and ethylene/vinyl alcoholcopolymer. Tie layers can be made from polymers such as polyolefin,modified polyolefin, ethylene/vinyl acetate copolymer, modifiedethylene/vinyl acetate copolymer, and homogeneous ethylene/alpha-olefincopolymer. Typical tie layer polymers include anhydride modified graftedlinear low density polyethylene, anhydride grafted low densitypolyethylene, anhydride grafted polypropylene, anhydride grafted methylacrylate copolymer, anhydride grafted butyl acrylate copolymer,homogeneous ethylene/alpha-olefin copolymer, and anhydride graftedethylene/vinyl acetate copolymer.

As used herein, the phrases “inner layer” and “internal layer” refer toany layer, of a multilayer film, having both of its principal surfacesdirectly adhered to another layer of the film.

As used herein, the phrase “outer layer” refers to any film layer havingless than two of its principal surfaces directly adhered to anotherlayer of the film. A multilayer film has two outer layers, each of whichhas a principal surface adhered to only one other layer of themultilayer film.

As used herein, the term “package” refers to packaging materialsconfigured around a product being packaged. The phrase “packagedproduct,” as used herein, refers to the combination of a product whichis surrounded by the package.

Once a multilayer film is heat sealed to itself or another member of thepackage being produced (i.e., is converted into a packaging article,e.g., a bag, pouch, or casing), one outer layer of the film is an insidelayer of the packaging article and the other outer layer becomes theoutside layer of the packaging article. The inside layer can be referredto as an “inside heat seal/product contact layer”, because this is thefilm layer that is sealed to itself or another article, and it is thefilm layer closest to the product, relative to the other layers of thefilm. The other outer layer can be referred to as the “outside layer”and/or as the “outer abuse layer” or “outer skin layer”, as it is thefilm layer furthest from the product, relative to the other layers ofthe multilayer film. Likewise, the “outside surface” of a packagingarticle (i.e., bag) is the surface away from the product being packagedwithin the bag.

As used herein, the term “bag” is inclusive of L-seal bags, side-sealbags, backseamed bags, and pouches. An L-seal bag has an open top, abottom seal, one side-seal along a first side edge, and a seamless(i.e., folded, unsealed) second side edge. A side-seal bag has an opentop, a seamless bottom edge, with each of its two side edges having aseal therealong. Although seals along the side and/or bottom edges canbe at the very edge itself, (i.e., seals of a type commonly referred toas “trim seals”), preferably the seals are spaced inward (preferably ¼to ½ inch, more or less) from the bag side edges, and preferably aremade using a impulse-type heat sealing apparatus, which utilizes a barwhich is quickly heated and then quickly cooled. A backseamed bag is abag having an open top, a seal running the length of the bag in whichthe bag film is either fin-sealed or lap-sealed, two seamless sideedges, and a bottom seal along a bottom edge of the bag. A pouch is madefrom two films sealed together along the bottom and along each sideedge, resulting in a U-seal pattern. Several of these various bag typesare disclosed in U.S. Pat. No. 6,790,468, to Mize et al, entitled “PatchBag and Process of Making Same”, the entirety of which is herebyincorporated by reference. In the Mize et al patent, the bag portion ofthe patch bag does not include the patch. Packages produced using aform-fill-seal process are disclosed in U.S. Pat. No. 4,589,247, hereinincorporated, in its entirety, by reference thereto.

While the multilayer heat-shrinkable film can be sealed to itself toform a bag, optionally, a heat-shrinkable patch film can be adhered tothe bag. The bag film and/or the patch film can comprise at least onesemi-crystalline polyamide selected from the group consisting ofpolyamide 6, polyamide 66, polyamide 6/66, and polyamide 6/12, with theat least one semi-crystalline polyamide making up at least 50 weightpercent of at least one layer of the film, based on total layer weight.The bag film and/or the patch film can have a total free shrink at 185°F. of at least 35 percent as measured using ASTM D-2732. The bag filmand/or the patch film can have a total semi-crystalline polyamidecontent of at least 35 volume percent based on total film volume whereinthe semi-crystalline nylon is at least one member selected from thegroup consisting of polyamide 6, polyamide 66, polyamide 6/66, andpolyamide 6/12. In one embodiment, the bag film and/or patch film ismade by a process in accordance with the first aspect of the presentinvention.

Although seals along the side and/or bottom edges can be at the veryedge itself, (i.e., seals of a type commonly referred to as “trimseals”), preferably the seals are spaced inward (preferably ¼ to ½ inch,more or less) from the bag side edges, and preferably are made using aimpulse-type heat sealing apparatus, which utilizes a bar which isquickly heated and then quickly cooled.

While the multilayer heat-shrinkable film can be sealed to itself toform a bag, optionally, a heat-shrinkable patch film can be adhered tothe bag. The patch film can comprise at least one semi-crystallinepolyamide selected from the group consisting of polyamide 6, polyamide66, polyamide 6/66, and polyamide 6/12, with the at least onesemi-crystalline polyamide making up at least 50 weight percent of atleast one layer of the film, based on total layer weight. The patch filmcan have a total free shrink at 185° F. of at least 35 percent asmeasured using ASTM D-2732. The patch film can have a totalsemi-crystalline polyamide content of at least 35 volume percent basedon total film volume wherein the semi-crystalline nylon is at least onemember selected from the group consisting of polyamide 6, polyamide 66,polyamide 6/66, and polyamide 6/12. In one embodiment, the patchcomprises a multilayer heat-shrinkable film in accordance with the firstaspect of the present invention.

Casings are also included in the group of heat-shrinkable packagingarticles. Casings include seamless tubing casings which have clipped orsealed ends, as well as backseamed casings. Backseamed casings includelap-sealed backseamed casings (i.e., backseam seal of the inside layerof the casing to the outside layer of the casing, i.e., a seal of oneouter film layer to the other outer film layer of the same film),fin-sealed backseamed casings (i.e., a backseam seal of the inside layerof the casing to itself, with the resulting “fin” protruding from thecasing), and butt-sealed backseamed casings in which the longitudinaledges of the casing film are abutted against one another, with theoutside layer of the casing film being sealed to a backseaming tape.Each of these embodiments is disclosed in U.S. Pat. No. 6,764,729 B2, toRamesh et al, entitled “Backseamed Casing and Packaged ProductIncorporating Same, which is hereby incorporated in its entirety, byreference thereto.

The term “polymer”, as used herein, is inclusive of homopolymer,copolymer, terpolymer, etc. “Copolymer” includes copolymer, terpolymer,etc. As used herein, terms such as “polyamide”, “polyolefin”,“polyester”, etc are inclusive of homopolymers of the genus, copolymersof the genus, terpolymers of the genus, etc, as well as graft polymersof the genus and substituted polymers of the genus (e.g., polymers ofthe genus having substituent groups thereon).

As used herein, the phrase “heterogeneous polymer” refers topolymerization reaction products of relatively wide variation inmolecular weight and relatively wide variation in compositiondistribution, i.e., typical polymers prepared, for example, usingconventional Ziegler-Natta catalysts. Heterogeneous copolymers typicallycontain a relatively wide variety of chain lengths and comonomerpercentages. Heterogeneous copolymers have a molecular weightdistribution (Mw/Mn) of greater than 3.0.

As used herein, the phrase “homogeneous polymer” refers topolymerization reaction products of relatively narrow molecular weightdistribution and relatively narrow composition distribution. Homogeneouspolymers are useful in various layers of the multilayer heat-shrinkablefilm. Homogeneous polymers are structurally different from heterogeneouspolymers, in that homogeneous polymers exhibit a relatively evensequencing of comonomers within a chain, a mirroring of sequencedistribution in all chains, and a similarity of length of all chains,i.e., a narrower molecular weight distribution. Furthermore, homogeneouspolymers are typically prepared using metallocene, or other single-sitetype catalysis, rather than using Ziegler Natta catalysts.

As used herein, the term “polyamide” refers to a polymer having amidelinkages, more specifically synthetic polyamides, either aliphatic oraromatic, either in semi-crystalline or amorphous form. It is intendedto refer to both polyamides and co-polyamides. The polyamides arepreferably selected from nylon compounds approved for use in producingarticles intended for use in processing, handling, and packaging food,including homopolymers, copolymers and mixtures of the nylon materialsdescribed in 21 C.F.R. 177.1500 et seq., which is incorporated herein byreference. Exemplary of such polyamides include nylon homopolymers andcopolymers such as those selected from the group consisting of nylon 4,6(poly(tetramethylene adipamide)), nylon 6 (polycaprolactam), nylon 6,6(poly(hexamethylene adipamide)), nylon 6,9 (poly(hexamethylenenonanediamide)), nylon 6,10 (poly(hexamethylene sebacamide)), nylon 6,12(poly(hexamethylene dodecanediamide)), nylon 6/12(poly(caprolactam-co-laurallactam)), nylon 6,6/6 (poly(hexamethyleneadipamide-co-caprolactam)), nylon 6/66(poly(caprolactam-co-hexamethylene adipamide)), nylon 66/610 (e.g.,manufactured by the condensation of mixtures of nylon 66 salts and nylon610 salts), nylon 6/69 resins (e.g., manufactured by the condensation ofepsilon-caprolactam, hexamethylenediamine and azelaic acid), nylon 11(polyundecanolactam), nylon 12 (polyauryllactam), nylon MXD6, nylonMXDI, nylon 6I/6T, and copolymers or mixtures thereof.

As used herein, the phrase “. . . a distance of from X to Y inchesdownstream of the annular die . . . ”, and the like, refer to a distancemeasured from the point at which the extrudate emerges from the die tothe downstream point at which the water ring is positioned and/or thestream of quenching liquid first comes into contact with the extrudateemerging from the die.

As used herein, the phrase “. . . the semi-crystalline polyamidecomprising at least one member selected from the group consisting ofpolyamide 6, polyamide 66, polyamide 6/66, and polyamide 6/12, with thesemi-crystalline polyamide making up at least X volume percent of theannular extrudate, based on total extrudate volume . . . ”, and thelike, means that, if only one of the semi-crystalline polyamides ispresent, it must be present in the film in an amount that makes up atleast X volume percent, based on total film volume. If thissemi-crystalline polyamide is present in more than one layer of thefilm, the amount of the semi-crystalline polyamide in the film is thesum of the amounts of the semi-crystalline polyamide in each of thevarious layers of the film in which that member is present. If more thanone of the semi-crystalline polyamides is present in the film, thephrase means that by adding together the respective volume percent(s) ofeach of the semi-crystalline polyamides present in the film, theresulting sum total of all of the volume percents of thesemi-crystalline polyamides must make up at least X volume percent ofthe film, based on total film volume. In this latter case, no onesemi-crystalline polyamide must be present in the film in an amount ofat least X volume percent, based on total film volume.

As used herein, a phrase such as “. . . the semi-crystalline polyamidecomprising at least one member selected from the group consisting ofpolyamide 6, polyamide 66, and polyamide 6/66, and polyamide 6/12,wherein the at least one semi-crystalline polyamide makes up at least Xweight percent of the layer . . . ”, and the like, means that if onlyone of the semi-crystalline polyamides is present in a layer, it must bepresent in the layer in an amount that makes up at least X weightpercent of the layer, based on total layer weight. If more than one ofthe semi-crystalline polyamides is present in the layer, by addingtogether the respective weight percent of each semi-crystallinepolyamide present in the layer, the resulting sum total of all of theweight percents of the semi-crystalline polyamides present in the layermust make up at least X weight percent of the layer, based on totallayer weight. In this latter case, no one semi-crystalline polyamidemust be present in the layer in an amount of at least X weight percent,based on total layer weight.

At least one layer of the heat-shrinkable film can contain thesemi-crystalline polyamide can make up at least 5 weight percent of thesecond layer, based on total layer weight. Alternatively, thesemi-crystalline polyamide can make up at least 10 weight percent, or atleast 15 weight percent, or at least 20 weight percent, or at least 30weight percent, or at least 40 weight percent, or at least 50 weightpercent, or at least 60 weight percent, at least 70 weight percent, atleast 80 weight percent, at least 90 weight percent, or even up to 100weight percent of the second layer, based on total layer weight.

The film can comprise at least one semi-crystalline polyamide selectedfrom the group consisting of polyamide 6/12 having a melting point of atleast 135° C., polyamide 6, polyamide 66, polyamide 6/66. Alternatively,the film can comprise at least one semi-crystalline polyamide selectedfrom the group consisting of polyamide 6/12 having a melting point of atleast 165° C., polyamide 6, polyamide 66, polyamide 6/66.

The semi-crystalline polyamide can be present in the multilayer film inan amount of at least 35 volume percent, based on total film volume.Alternatively, the semi-crystalline polyamide can be present in themultilayer film in an amount of at least 40 volume percent of the film,or at least 45 percent, or at least 50 volume percent, or at least 55volume percent, or at least 60 volume percent, or at least 65 volumepercent, or at least 70 volume percent, or at least 75 volume percent,or at least 80 volume percent, or at least 85 percent, or at least 90volume percent, or at least 95 volume percent, based on total filmvolume.

The process can be used to produce an annular extrudate comprisingpolyamide in an amount of at least 85 percent, based on total extrudatevolume; or at least 90 percent based on total extrudate volume, or atleast 95 percent based on total extrudate volume, or at least 98 percentbased on total extrudate volume, or at least 99 percent based on totalextrudate volume, or 100 percent based on total extrudate volume.

The process can be used to produce a heat-shrinkable film having a firstlayer which serves as an outer seal layer, and a second layer comprisingat least one semi-crystalline polyamide having a melt point above 215°C. The first layer can comprise at least one member selected from thegroup consisting of: (i) a semi-crystalline polyamide having a meltingpoint of up to 215° C.; and (ii) a blend of a semi-crystalline polyamidehaving a melting point above 215° C. with (a) an amorphous polyamide or(b) a semi-crystalline polyamide having a melting point of up to 215° C.The second layer can comprise a blend of the semi-crystalline polyamidehaving a melt point above 215° C. with at least one member selected fromthe group consisting of polyamide 6/12 having a melt point below 215°C., polyamide 6/69, polyamide MXD6, polyamide 66/610, and amorphouspolyamide.

The semi-crystalline polyamide can be a primary component present in ablend with a secondary component that comprises at least one memberselected from the group consisting of polyamide 6/69, polyamide MXD6,polyamide MXDI, polyamide 66/610, amorphous polyamide (includingpolyamide 6I/6T), polyether block amide copolymer, polyester (includingpolyethylene terephthalate/glycol), EVOH, polystyrene, polyolefin (e.g.,polybutene, long chain branched homogeneous ethylene/alpha-olefincopolymer, and linear low density polyethylene), and ionomer resin.While the primary component can be present in the blend in an amount offrom 60 to 99 weight percent, based on total blend weight, the secondarycomponent can be present an amount of from about 1 to 40 percent, basedon total blend weight; or the primary component can be present in anamount of from 85 to 98 weight percent, with the secondary component ispresent in an amount of from 2 to 15 weight percent, based on a totalblend weight.

Various multilayer embodiments can be made using the process of theinvention, including:

-   -   seal/polyamide    -   seal/tie/polyamide/barrier    -   seal/first tie/polyamide/barrier/second tie/second outer    -   seal/first tie/first polyamide/barrier/second polyamide    -   seal/first tie/polyamide/barrier/second tie/second outer    -   seal/first tie/first polyamide/barrier/second polyamide/second        tie/second outer.    -   1^(st) Outer/1^(st) tie/1^(st) Core/2^(nd) tie/Barrier/2^(nd)        Core/3^(rd) tie/2^(nd) Outer        These films can be fully coextruded, or prepared using an        extrusion-coating process. In the last film in the above        listing, the first outer layer, first tie layer, first core        layer, and second tie layer can be coextruded as a four-layer        multilayer substrate tape, with the barrier layer, second core        layer, third tie layer, and second outer layers being        extrusion-coated over the substrate tape as a four-layer        multilayer coating. Optionally, the substrate tape can be        irradiated before the additional layers are extrusion coated        onto the substrate tape. Irradiation produces a stronger polymer        network by crosslinking the polymer chains. Extrusion-coating        allows a portion of the final multilayer structure to be        strengthened by irradiation, while the extrusion-coating of the        substrate allows the use of polyvinylidene chloride as the        barrier layer, without subjecting the polyvinylidene chloride to        irradiation. Irradiation of polyvinylidene chloride is        undesirable because irradiation can cause degradation of        polyvinylidene chloride.

In the multilayer, heat-shrinkable film, all of the film layers can bearranged symmetrically with respect to the polymeric composition of eachfilm layer. In addition, all of the film layers can be arrangedsymmetrically with respect to both composition and thickness. In oneembodiment, the seal layer is thicker than the second outer layer. Theseal layer can have a thickness of from 110% to 300% of the thickness ofthe second outer layer, or from 150% to 250% of the thickness of thesecond outer layer.

In one embodiment, the film is annealed. In an alternative embodiment,the film is not annealed. Annealing can be carried out by reheating thefilm via conduction, convection, or irradiation. For example, annealingcan be carried out by passing the film in partial wrap around one ormore heated rollers, or by subjecting the film to infrared irradiation.An annular film can be reinflated and annealed while reinflated. Onemethod of annealing is to pass the film in partial wrap around one ormore heated rollers. For example, the film to be annealed can be passedin partial wrap around 4 rollers, each having a diameter of from 3-30inches, with the film being wrapped from about 45 to 225 degrees aroundeach roller, with the rollers being positioned close to one another sothat the film travels from 2 to 30 inches between rollers, with each ofthe annealing rollers providing a metal surface heated to a temperatureof from 100° F. to 200° F. In addition, one or more cooling rollers canoptionally be provided immediately downstream of the annealing rollers,to cool and stabilize the film.

The film of the invention is a heat-shrinkable film. The film can beproduced by carrying out only monoaxial orientation, or by carrying outbiaxial orientation. As used herein, the phrase “heat-shrinkable” isused with reference to films which exhibit a total free shrink (i.e.,the sum of the free shrink in both the machine and transversedirections) of at least 10% at 185° F., as measured by ASTM D 2732,which is hereby incorporated, in its entirety, by reference thereto. Allfilms exhibiting a total free shrink of less than 10% at 185° F. areherein designated as being non-heat-shrinkable. The heat-shrinkable filmcan have a total free shrink at 185° F. of at least 15%, or at least20%, or at least 30%, or at least 40%, or at least 45%, or at least 50%,or at least 55%, or at least 60%, or at least 65%, or at least 70%, asmeasured by ASTM D 2732. Heat shrinkability can be achieved by carryingout orientation in the solid state (i.e., at a temperature below theglass transition temperature of the polymer). The total orientationfactor employed (i.e., stretching in the transverse direction anddrawing in the machine direction ) can be a any desired factor, such asat least 2×, at least 3×, at least 4×, at least 5×, at least 6×, atleast 7×, at least 8×, at least 9×, at least 10×, at least 16×, or from1.5× to 20×, from 2× to 16×, from 3× to 12×, or from 4× to 9×.

Film transparency (also referred to herein as film clarity) was measuredin accordance with ASTM D 1746-97 “Standard Test Method for Transparencyof Plastic Sheeting”, published April, 1998, which is herebyincorporated, in its entirety, by reference thereto. The results arereported herein as “percent transparency”. The multilayer,heat-shrinkable film can exhibit a transparency of at least 15 percent,or at least 20 percent, or at least 25 percent, or at least 30 percent,measured using ASTM D 1746-97.

Film haze values were measured in accordance with ASTM D 1003-00“Standard Test Method for Haze and Luminous Transmittance of TransparentPlastics”, published July 2000, which is hereby incorporated, in itsentirety, by reference thereto. The results are reported herein as“percent haze”. The multilayer, heat-shrinkable film can exhibit a hazeof less than 7.5 percent, or less than 7 percent, or less than 6percent, measured using ASTM D 1003-00.

Film gloss values were measured in accordance with ASTM D 2457-97“Standard Test Method for Specular Gloss of Plastic Films and SolidPlastics”, published Jan. 10, 1997, which is hereby incorporated, in itsentirety, by reference thereto. The results are reported herein as“percent gloss”. The film can exhibit a gloss, as measured using ASTM D2457-97, of from 60% to 100%, or from 70% to 90%.

In one embodiment, the film does not comprise a crosslinked polymernetwork. In another embodiment, the film comprises a crosslinked polymernetwork. Optionally, the film can be irradiated to induce crosslinkingof polymer, particularly polyolefin in the film. The relatively highcontent of polyamide in the film provides a high level of toughness andimpact strength, and as a result reduces the need to crosslink anypolyolefin that may be present in the film. However, the film can besubjected to irradiation using an energetic radiation treatment, such ascorona discharge, plasma, flame, ultraviolet, X-ray, gamma ray, betaray, and high energy electron treatment, which induce cross-linkingbetween molecules of the irradiated material. The irradiation ofpolymeric films is disclosed in U.S. Pat. No. 4,064,296, to BORNSTEIN,et. al., which is hereby incorporated in its entirety, by referencethereto. BORNSTEIN, et. al. discloses the use of ionizing radiation forcrosslinking polymer present in the film.

Radiation dosages are referred to herein in terms of the radiation unit“RAD”, with one million RADS, also known as a megarad, being designatedas “MR”, or, in terms of the radiation unit kiloGray (kGy), with 10kiloGray representing 1 MR, as is known to those of skill in the art. Asuitable radiation dosage of high energy electrons is in the range of upto about 16 to 166 kGy, more preferably about 30 to 90 kGy, and stillmore preferably, 30 to 50 kGy. Preferably, irradiation is carried out byan electron accelerator and the dosage level is determined by standarddosimetry processes. Other accelerators such as a van der Graaf orresonating transformer may be used. The radiation is not limited toelectrons from an accelerator since any ionizing radiation may be used.

The film of the invention can be produced as a fully coextruded film,i.e., all layers of the film emerging from a single die at the sametime. Alternatively, the film can be produced using an extrusion coatingprocess in accordance with U.S. Pat. No. 4,278,738, to Brax et al, whichis hereby incorporated, in its entirety, by reference thereto.

Viewing FIG. 1, FIG. 2A, FIG. 2B, FIG. 2C, and FIG. 3 together, aheat-shrinkable film is prepared by feeding solid polymer beads (notillustrated) to a plurality of extruders 52 (for simplicity, only oneextruder is illustrated). Inside extruders 52, the polymer beads areforwarded, melted, and degassed, following which the resultingbubble-free melt is forwarded and extruded through annular die 56,resulting in annular extrudate 58.

Shortly after exiting die 56, annular extrudate 58 is drawn downwardtoward cylindrical air shoe 60. While the outside diameter of air shoe60 can be the same size as the diameter of the orifice of annular die 56as illustrated in FIG. 1 and FIG. 2C, the annular extrudate 58 can beallowed to draw down (i.e., while it remains molten, extrudate 58 canundergo diameter reduction, also referred to as “necking-in”) if theoutside diameter of air shoe 60 is smaller than the orifice of annulardie 56. The extent of neck-in of annular extrudate 58 is limited by theoutside diameter of air shoe 60, as illustrated in FIG. 2A. Thenecking-in of annular extrudate 58 is increased by drawing extrudate 58downward at a speed greater than the speed at which the molten polymeremerges from annular die 56. The downward drawing of annular extrudate58 generates tension, and results in a more stable process. Thisincrease in process stability produces greater width uniformity in theannular extrudate 58, greater thickness uniformity in the annularextrudate 58, and improved downstream processability as the variousprocessing operations are carried out on a more uniform annularextrudate 58. Moreover, this greater uniformity in annular extrudate 58results in more uniform product characteristics, such as more uniformimpact strength, more uniform shrink, more uniform optics, etc. Annularextrudate 58 can neck down so that its inside diameter (i.e., upon beingquenched) decreases by at least 10%, at least 20%, at least 30%, atleast 40%, or even at least 50% compared with its diameter at the pointat which it emerges from annular die 56.

Alternatively, the extrudate can be supported in a manner so that theextrudate is prevented from necking-in as it emerges from the die, asillustrated in FIG. 1 and in FIG. 2C. In the process illustrated inFIGS. 1 and 2C, air shoe 60 is positioned over hollow pipe 62 thatpasses through die 56 and the hollow center of air shoe 60. Air shoe 60has an outside diameter large enough that annular extrudate 58 issupported and is prevented from substantially necking-in upon emergencefrom annular die 56. The outer surface of air shoe 60 is roughened with80-grit sandpaper. Integral with air shoe 60 is upper flange 64 thereof,which is bolted to the bottom surface of die 56.

In use, pressurized air line 68 supplies cooled, pressurized air to aninterior chamber within air shoe 60. The air supplied to air shoe 60 canhave a temperature of from 45° F. to 80° F., and preferably has atemperature of about 60° F. The pressurized air supplied to air shoe 60from air line 68 initially flows into the interior chamber within airshoe 60, and thereafter flows radially outward through a plurality ofholes 76 toward the inside surface 86 of annular extrudate 58. Holes 76preferably have a diameter of about 0.030 inch, and are preferablyspaced uniformly over the surface of air shoe 60, with each hole 76being about 0.563 inch from its nearest neighbor, in a pattern so thateach hole 76 is surrounded by a maximum of 6 additional holes 76.

Shortly after the emergence of annular extrudate 58 from die 56,downward-moving annular extrudate 58 is rapidly quenched by contact withan annular stream 80 of cool water emitted from a gap in annular waterring 78. The gap in annular water ring 78 can have a width of from about0.02 to about 0.5 inch, or from 0.03 to 0.3 inch, or from 0.05 to 0.25inch, or from 0.07 to 0.16 inch. Annular stream 80 contacts outsidesurface 88 of annular extrudate 58, with annular stream 80 travelingdownward on the exterior surface of annular extrudate 58 as cascadingwater 82. Annular stream 80 contacts outside surface 88 of annularextrudate 58 within a distance of from 0.1 inch to 8 inches downstreamof the annular die.; or within a distance of from 0.5 inch to 5 inches;or within a distance of from 0.5 inch to 3 inches, or within a distanceof from 1 to 3 inches.

Annular stream 80 of cool water, which becomes cascading cool water 82,quickly draws heat from annular extrudate 58, and thereby quicklyquenches (i.e., solidifies) the polymers making up annular extrudate 58.In fact, annular stream 80 and cascading water 82 draw heat from annularextrudate 58 so quickly that the semi-crystalline polyamide withinannular extrudate 58 solidifies before it has an opportunity to undergosubstantial crystallization. It has been discovered that the quenchingis carried out so rapidly that the semi-crystalline polyamide in annularextrudate 58 is frozen in a state in which it is more readily orientedto make a heat-shrinkable film.

Although annular stream 80 and cascading water 82 are the primarysources for the rapid quenching of annular extrudate 58, the cool airemitted from air shoe 60 also serves to quench annular extrudate 58 fromthe inside out. However, the primary purpose of the air emitted from airshoe 60 is to provide a slightly superatmospheric pressure withinannular extrudate 58, in order to prevent the collapse of annularextrudate 58 as it is contacted by annular stream 80 of cool water whichbecomes cascading water 82. The cool air emitted from holes 76 in airshoe 60 emerges from air shoe 60 into narrow gap 90 between the outsidesurface 84 of air shoe 60 and the interior surface 86 of annularextrudate 58. Gap 90 is typically only from about 0.001 to about 0.5inch wide, more commonly from 0.001 to 0.05 inch wide. The flow of coolair emitted from holes 76 is downward toward and into open end 92 ofhollow pipe 62. The cool air then travels upward through hollow pipe 62and through the open center of die 56, with the cool air being evacuatedinto the environment.

Annular extrudate 58 and cascading water 82 both travel downward towardsnip rollers 92. Cascading water 82 flows into catch basin 91, and isthereafter recycled through pump and cooling means 89, with the recooledwater being recirculated to annular water ring 56.

As annular extrudate 58 passes through nip rollers 93, annular extrudate58 is reconfigured from an inflated configuration to a lay-flatconfiguration. The resulting reconfigured lay-flat annular extrudate 94is thereafter wound up on a reel (not illustrated). Optionally, lay-flatannular extrudate 94 can be fed through irradiation vault 96 surroundedby shielding 98, where annular extrudate 94 is irradiated with highenergy electrons (i.e., ionizing radiation) from iron core transformeraccelerator 100. Annular extrudate 94 can be guided through irradiationvault 96 on a series of rollers 102. Preferably, the irradiation oflay-flat annular extrudate 94 is at a level of from about 2 to 10megarads (hereinafter “MR”), after which lay-flat annular extrudate 94is wound up on reel 95 as irradiated lay-flat annular extrudate 104.

As a second step of the process, the wound up, irradiated, lay-flatannular extrudate 104 is unwound and directed over guide roller 106,after which irradiated annular extrudate 104 is passed into and throughhot water 108 in tub 110 containing hot water 108. While the temperatureof hot water 108 can be from about 125° F. to about 212° F., or from130° F. to 21020 F., or from 130° F. to 180° F., or from 160° F. to 190°F., or from 145° F. to 175° F., or from 150° F. to 170° F., hot water108 is preferably maintained at a temperature of about 175° F. Annularextrudate 104 is forwarded into and through hot water 108 so that itremains immersed in hot water 108 for a period of from about 0.25 secondto about 80 seconds, or from 1 to 40 seconds, or from 2 to 10 seconds,or from 3 to 7 seconds, or from 0.5 to 4 seconds, or from 1 to 3seconds. Preferably, annular extrudate 104 is immersed for a period offrom about 1 to 2 seconds. It is preferred to immerse annular extrudate104 in hot water 108 for the minimum time necessary to bring annularextrudate 104 up to the desired temperature for solid state biaxialorientation.

Upon emergence from hot water 108, annular extrudate 104 passes throughlower set of nip rollers 110, and through annular air ring 112 asannular extrudate 104 is pulled upward by upper set of nip rollers 116.Annular air ring 112 is supplied with cool, compressed air at atemperature of from 45° F. to about 90° F., or from 30° F. to 120° F.,or a temperature of about 60° F. The cool air is supplied to air ring112 from a plurality of air lines, each air line providing cool air at apressure of up to 150 psi.

Upon emergence from lower nip rollers 110, annular extrudate 104 issolid-state oriented in both the machine direction and the transversedirection as it moves upward and passes around a trapped air bubble 114,and towards upper nip rollers 116. The surface speed of upper niprollers 116 is greater than the surface speed of lower nip rollers 110.The solid state orientation stretches annular extrudate 104 in both themachine direction and the transverse direction, resulting in theformation of biaxially-oriented, heat-shrinkable film 118.

FIG. 3 provides an enlarged, detailed, cross-sectional view of annularextrudate 104 at the point in the process at which extrudate 104 passesthrough air ring 112. Air ring 112 is an assembly of upper ring 111 anda lower ring which is an assembly of cap member 113 bolted to platemember 115 and air permeable insert 117. Air permeable insert 117 can bedesigned of sintered metal, such as sintered bronze. Another air ringcapable of the performance of the sintered bronze is an air ring insertsuch as the microbored air ring insert available from Future Design,Inc, at 5369 Maingate Drive, Mississauga, Ontario, Canada LW4 1G6 (webaddress of www.saturn2.com). The sintered bronze and microbored air ringinserts are both microporous, due to the sintered metal design or due tomicro bored holes therein (hole diameter within the range of from 0.002to 0.02 inch, or from 0.005 to 0.01 inch).

Compressed air (at 20 to 150 psi) passing through porous insert 117 issupplied to chamber 119 by air lines 121. Pressurized air in chamber 119enters passageway 123 and passes outward and down, around the outside ofextrudate 104. The effect of the airstream passing downward and aroundextrudate 104 is to pull trapped bubble 114 of air downward, to preventtrapped bubble 114 from moving upward and bursting oriented film 118.Simultaneously, a fan supplies air to the region between plate member115 and upper ring 111, this air passing between the inside edge 125 ofupper ring 111 and the outside concave surface 127 of plate member 115.This air passes out of air ring 112 and around extrudate 104 asextrudate 104 is being oriented. The effect of this second airstream isto pass upward and around extrudate 104 to push trapped bubble 114upward, the prevent trapped bubble 114 from moving downward and into airring and onward toward lower nip rollers 110, which likewise would beproblematic for continuation of the process. In this manner, air ring112 provides opposing airstreams to stabilize the lower position oftrapped bubble 114. As can also be seen in FIG. 3, as extrudate 104 isoriented to produce heat-shrinkable, film 118, it thins down from thethickness of the tape to the final film thickness.

As a result of the transverse stretching and longitudinal drawing ofannular extrudate 104, irradiated, biaxially-oriented, heat-shrinkablefilm 118 is produced. Heat-shrinkable film 118 has been drawn in thelongitudinal direction in the solid state, and stretched in thetransverse direction in the solid state, in at a total orientation ratio(i.e., L+T) of from about 1:2 to about 1:20, or from 1:2.5 to 1:16, orfrom 1:4 to 1:14, or about 1:9. The result is a biaxial oriented,heat-shrinkable film.

As annular, heat-shrinkable film 118 approaches upper nip rollers 116,it is collapsed into lay-flat configuration by rollers 120, thereafterpassing between nip rollers 116. Heat-shrinkable film 118 is thenforwarded over guide roller 122, and then rolled onto wind-up roller124. Idler roller 126 assists with wind-up. While not illustrated,annealing rollers and cooling rollers can optionally be provided betweennip rollers 116 and wind up roller 124.

The amount of solid state orientation of annular extrudate 104, and theease of solid state orientation of annular extrudate 104, issignificantly affected by a variety of factors. It is the relativelyhigh proportion of semi-crystalline polyamide in the annular extrudatethat makes the annular extrudate difficult to orient in the solid state.However, the process described above provides several features thatsignificantly improve the ability to orient such an annular extrudate.The first factor is the rapid quenching of the annular extrudate as itemerges from the die. A second factor is the relatively low temperatureof hot water 108. A third factor is the relatively low immersion time ofannular extrudate 104 in hot water 108. A fourth factor is therelatively rapid cooling of the heated annular extrudate 104 by air ring112 upon emergence of annular extrudate 104 from hot water 108. Therapid quenching, the reheating to a relatively low temperature for arelatively short time and the rapid cooling upon emergence from thewater bath all assist in enhancing the amount of solid stateorientation, and the ease of the solid state orientation. They alsoassist in lowering the temperature at which the solid state orientationoccurs. Lowering the temperature at which the solid state orientationoccurs produces a film that is heat-shrinkable at a lower temperature. Alower shrink temperature is advantageous for the packaging ofheat-sensitive products, because less heat is required to shrink thefilm tight against the product, thereby providing an attractive tightpackage appearance while exposing the heat-sensitive product to lessheat during the heat shrinking of the film tight around the product.

It is believed that each of the four factors impair the crystallizationof the semi-crystalline polyamide, which makes the extrudate easier toorient in the solid state. It has been found that this process alsoproduces a heat-shrinkable film having a high total free shrink at 185°F. together with low haze and high clarity, in spite of the presence ofa relatively high proportion of semi-crystalline polyamide in theresulting heat-shrinkable film 116.

FIG. 4 illustrates a one-step process for making the heat-shrinkablefilm. In the process of FIG. 4, all equipment and steps are the same asthe two-step process of FIG. 1, except that the annular extrudate 104 isnot wound up after irradiation and thereafter unwound before solid stateorientation. Rather, annular extrudate 104 emerges from irradiationvault 96 and is then forwarded directly into hot water 108. Otherwise,all of the enumerated components of the process illustrated in FIG. 4correspond with the components described above with reference to FIGS.1, 2, and 3. While not illustrated, optional annealing rollers andcooling rollers be provided between nip rollers 116 and wind up roller124.

FIG. 5 illustrates a two-step process for producing an extrusion-coated,heat-shrinkable film. In the process of FIG. 5, all equipment and stepsare the same as the two-step process illustrated in FIGS. 1, 2, and 3 asdescribed above, except that annular extrudate 58 serves as a substrateonto which one or more additional layers are extrusion coated with acoating of one or more film layers.

More particularly, after the optional irradiation of annular extrudate58 (i.e., annular substrate 58), annular irradiated extrudate 94 (i.e.,annular irradiated substrate 94) is directed to nip rollers 130 while inlay-flat configuration. Immediately downstream of nip rollers 130,annular irradiated substrate 94 is reconfigured from lay-flatconfiguration to round configuration by being directed around trappedair bubble 132 which extends from nip rollers 130 to nip rollers 134.The resulting round annular substrate 94 is then directed through vacuumchamber 136, immediately following which round annular substrate 94 ispassed through extrusion coating die 138, which extrudes coating stream140 over and around the outside surface of round annular substrate 94,resulting in round extrusion coated extrudate 142, which is then passedthrough and cooled by a second water ring 144 and thereafter forwardedthrough nip rollers 134 at which time round extrusion coated extrudate142 is reconfigured into lay-flat configuration and wound up on roll146. Second water ring 144 can be positioned from about 1 to 6 inchesdownstream of extrusion coating die 138, or from about 2 to 5 inchesdownstream of die 138. A stream of cool water (e.g., at 7.2° C., notillustrated) is emitted from second water ring 144, with this stream ofcool water flowing onto the exterior surface of extrusion-coated tape142, in order to rapidly quench the hot coating layers, particularly toretard crystallization of any semi-crystalline polyamide present ineither the coating layers or the substrate layers.

Annular extrudate 94 is not significantly drawn (either longitudinallyor transversely) as it is directed around trapped air bubble 132. Thesurface speed of downstream nip rollers 134 is about the same as thesurface speed of upstream nip rollers 130. Furthermore, annularextrudate 94 is inflated only enough to provide a substantially circulartubing without significant transverse orientation, i.e., withouttransverse stretching. Further details of the above-described coatingstep are generally as set forth in U.S. Pat. No. 4,278,738, to BRAX et.al., which is hereby incorporated by reference thereto, in its entirety.Otherwise, all of the enumerated components of the process illustratedin FIG. 5 correspond with the components described above with referenceto FIGS. 1, 2, and 3.

In the second step of the two-step process of FIG. 5, roll 146 istransported to a location for solid-state orientation, and is thereunwound so that irradiated extrudate 94 passes into hot water 108 and isthereafter biaxially oriented (and optionally annealed) in the samemanner as illustrated in FIGS. 1, 2A, 2B, and 3, described above. Whilenot illustrated, annealing rollers and cooling rollers can optionally beprovided between nip rollers 116 and wind up roller 124.

FIG. 6 is a schematic of a heat-shrinkable end-seal bag 160 in lay-flatconfiguration. End-seal bag 160 is made from the heat-shrinkable film.FIG. 7 is a cross-sectional view of bag 160 taken through section 7-7 ofFIG. 6. Viewing FIGS. 6 and 7 together, bag 160 comprises bag film 162,top edge 164 defining an open top, first bag side edge 166, second bagside edge 168, bottom edge 170, and end seal 172.

FIGS. 8 and 9 together illustrate heat-shrinkable side-seal bag 180 inlay-flat configuration. Side-seal bag 180 is made from theheat-shrinkable film. FIG. 9 is a cross-sectional view of bag 180 takenthrough section 9-9 of FIG. 8. Viewing FIGS. 8 and 9 together, side-sealbag 180 is made from bag film 182 which is heat sealed to itself. Sideseal bag 180 has top edge 184 defining an open top, bottom edge 190,first side seal 192, and second side seal 194.

Although not illustrated, a heat-shrinkable pouch can be made from twoseparate pieces of film. Unlike the end-seal and side-seal bagsdescribed above, the pouch is made by heat sealing two separate piecesof film together, with the pouch having an open top, a first side seal,a second side seal, and a bottom seal.

In all of the examples below, unless otherwise indicated, the extrudateis to be (or was) quenched using a water ring that emitted a flow ofwater onto the extrudate, with the flow of water cascading down theextrudate. In these examples, approximately 100% of the water emitted bythe water ring contacts (or contacted) the extrudate and cascades (orcascaded) down the extrudate for a distance of at least 24 inches.

RESINS UTILIZED IN THE EXAMPLES

Unless otherwise indicated, the following listing of resins identifiesthe various resins utilized in Examples 1-65 below. Examples 66-76 haveadditional tables designating the resins used therein.

Generic Resin Name Melt {additional Density Index Resin code Tradenameinformation} (g/cc) (dg/min) Supplier IONOMER Surlyn ® Zinc neutralizedethylene 0.980 11.5 DuPont AM7927 methacrylic acid copolymer + polyamideSSPE 1 Affinity ® Homogeneous 0.900 6.0 Dow 1280G ethylene/alpha-olefincopolymer SSPE 2 Affinity ® Homogeneous 0.900 3.0 Dow 1880Gethylene/alpha-olefin copolymer SSPE 3 Affinity ® EG Homogeneous 0.8680.5 Dow 8150G ethylene/octene copolymer SSPE 4 Affinity ® EG Homogeneous0.870 g/cc 0.99 Dow 8100G ethylene/octene copolymer SSPE5 Marflex ®Homogeneous 0.916 1.3 Chevron D143LP ethylene/hexane Phillips copolymerChemical VLDPE 1 Exceed ® Very low density 0.912 1.0 Exxon 1012polyethylene Mobil VLDPE 2 XUS Very low density 0.903 0.5 Dow 61520.15Lpolyethylene VLDPE 3 Attane ® 4203 Very low density 0.905 0.80 Dowpolyethylene VLDPE 4 Attane ® Very low density 0.904 3.91 Dow 4404Gpolyethylene VLDPE 5 Rexell ® Very low density 0.915 6.6 Huntsman V3401polyethylene VLDPE 6 ECD 364 VLDPE (ethylene/hexene 0.912 1.0 ExxonMobilcopolymer) LLDPE 1 Dowlex ® Linear Low Density 0.920 1.0 Dow 2045.03Polyethylene LLDPE 2 Ingenia ® amide wax in linear low 0.92 2 Ingenia1062 density polyethylene Polymers LLDPE 3 Exceed ® Linear low density0.918 4.5 Exxon 4518 polyethylene Mobil LMDPE 1 Dowlex ® heterogeneous0.935 2.5 Dow 2037 ethylene/octene copolymer PBTYL PB8640M Polybutylene0.908 1.0 Basell Polyolefins MA-LLD 1 Tymor ® 1203 Maleic anhydride0.906 1.7 Rohm & modified polyethylene Haas {blended with linear lowdensity polyethylene} MA-LLD 2 PX 3227 Maleic anhydride 0.913 1.7Equistar modified polyethylene Division {blended with linear low ofdensity polyethylene} Lyondell MA-EVA 1 Plexar ® Maleic Anhydride- 0.9303.2 Equistar, PX1007 Modified Ethylene/Vinyl Division Acetate Copolymerof Lyondell MA-EVA 2 Bynel ® 3861 Maleic Anhydride- 0.980 2.0 DuPontModified Ethylene/Vinyl Acetate Copolymer MA-EMA Bynel ®2174 MaleicAnhydride- 0.931 2.8 DuPont Modified Ethylene/Methyl Acrylate CopolymerNylon 1 Ultramid ® Polyamide 6 1.13 — BASF B40 Nylon 2 Selar ® 3426amorphous polyamide 1.19 — Dupont Nylon 3 Ultramid ® Polyamide 6 1.13 —BASF B50 Nylon 4 Grilon ® Polyamide 6/12 1.05 5.75 EMS- CF6S GrivoryNylon 5 Grilon ® CR9 Polyamide 6/12 1.12 — EMS Grivory Nylon 6 Grilon ®Polyamide 6/69 1.09 — EMS- BM13 SBGX Grivory Nylon 7 Ultramid ®Polyamide 6/66 1.12 — BASF C40 L01 Nylon 8 Pebax ® Polyamide 1.14 —Arkema mP1878 Nylon 9 Ultramid ® Polyamide 6 1.14 — BASF B40LN01 Nylon10 Grivory ® Polyamide MXD6/MXDI 1.2 g/cc 50.0 EMS- HB5299 GrivoryNatural Nylon 11 MXD6 Polyamide MXD6 1.22 0.5 Mitsubishi S6121 PolyesterNylon 12 Ultramid ® Polyamide 6/66 1.13 — BASF C33 01 Nylon 13 Grivory ®Amorphous polyamide 1.18 — EMS- G21 Natural Grivory Nylon 14 Vydyne ®Polyamide 66 1.14 — Solutia 65A Nylon 15 Ultramid ® Polyamide 6 1.14 —BASF B40LN01 Nylon 16 Grilon ® BM Polyamide 66/610 1.09 — EMS- 20 SBGGrivory Natural Nylon 17 Ultramid ® Polyamide 6 1.14 — BASF B33 01 Nylon18 UBE 6434B Polyamide 6/66/12 1.14 — UBE copolymer PET PET12822Polyethylene 1.40 — Eastman terephthalate Chemicals PETG PETG 6763Polyethylene 1.27 2.8 Eastman terephthalate/glycol Chemical EVA 1Escorene ® Ethylene/vinyl acetate 0.933 3.5 Exxon LD 713.93 copolymer(14.4% VA) Mobil EVA 2 PE 1651 Ethylene/vinyl acetate 0.928 0.5 Huntsmancopolymer (6.5% VA) EVA 3 Elvax ® 3128 ethylene/vinyl acetate 0.928 2.0Exxon copolymer (8.9% VA) Mobil EVA 4 Escorene ® Ethylene/vinyl acetate0.950 5.75 Exxon LD 761.36 copolymer (26.7% VA) Mobil EVA 5 Escorene ®Ethylene/vinyl acetate 0.935 0.4 Exxon LD 705.MJ copolymer (12.8% VA)Mobil EMA 1 EVAC SP Ethylene/methyl acrylate 0.944 2 Eastman 1305copolymer Chemical PU-A Purethane ® Solventless polyurethane 1.03 —Ashland A-1078 two part mixture Chemical CVAC and (adhesive) C-CAT 104EVOH 1 Eval ® LC- Saponified ethylene/ 1.14 5.5 Evalca/ E105A vinylacetate copolymer Kuraray {44 mol % ethylene} EVOH 2 EVAL ® Hydrolyzedethylene 1.20 3.9 Evalca/Kuraray L171B vinyl acetate copolymer (EVOHwith 27 mol % ethylene) PVdC Saran ® 806 Vinylidene chloride/ 1.69 — Dowmethyl acrylate copolymer ELAS 1 Kraton ® G Styrene-butadiene — — Kraton1657 elastomer Polymers ELAS 2 Kraton ® Styrene copolymer 1.01 2.0Kraton FG 1901 X Polymers STBL 1 NA 189 Copper iodide based 1.13 —Solutia stabilizer AB&S Grilon ® MB Antiblock and slip in 1.14 — EMS-3361 FS polyamide 6 Grivory Natural SLIP MB50-11 Polydimethylsiloxane in1.05 — Dow polyamide 6 Corning

Example 1

A coextruded multilayer heat-shrinkable film was produced utilizing theapparatus and process set forth in FIG. 1, described above. Themultilayer film had a total of 7 layers, in the following order, withthe thickness of each layer of the tape (i.e., prior to solid stateorientation) shown in mils being indicated below the layer identity andresin composition identification:

Example 1

Core Core 90% 90% Tie Nylon1 Nylon1 Tie Sealant MA- 10% Barrier 10% MA-Outer VLDPE1 LLD1 Nylon2 EVOH1 Nylon2 LLD1 VLDPE1 5 mils 1 mil 4 mils 1mil 4 mils 1 mil 5 mils

The extrudate was cast from an annular die (diameter of 12.7 cm), overan air shoe, and was rapidly quenched by 7.2° C. water emitted from awater ring positioned about 57 mm below the die. The air shoe had anoutside diameter of 8 cm and a length of 32 cm, and emitted cool air(15.6° C.) through 0.762 mm diameter holes spaced over the cylindricalsurface of the air shoe, the holes being spaced apart by a distance of14.3 mm, with the holes being arranged so that each hole inside thematrix of holes were surrounded by 6 holes. The airflow through theholes supported the film (so that it did not collapse) and cooled thefilm from the inside out, i.e., to assist in “freezing” the nylonquickly to minimize crystallization of the nylon. The pressure betweenthe air shoe and the film was slightly above atmospheric pressure (i.e.,about 780 mm Hg). The cool air was pumped into the hollow air shoe andout the holes, with the air then flowing down beneath the air shoe andthen up and out through a passageway through the center of the air shoe.

Although the air shoe assisted in freezing the nylon to minimize crystalformation, most of the heat in the extrudate was removed by contact withthe cool water (7.2° C.) emitted from the water ring, which waspositioned approximately 57 mm below the annular die. The resultingunirradiated, quenched tape was wound up onto a reel and transported toanother location for solid state orientation. The quenched tape wasunwound from the roll and forwarded into a hot bath heated to atemperature of 82° C. The tape remained in the hot bath for a period of2 seconds, following which the heated tape was immediately forwardedthrough a lower set of nip rollers followed by an upper set of niprollers, with the distance between the upper and lower sets of niprollers being about 1.8 meters. Between the upper and lower sets of niprollers, the tape was subjected to and solid state biaxial orientation.Orientation direction was produced by inflating the tape with a trappedbubble of air between the sets of nip rollers. Additional orientationwas provided by running the lower set of nip rollers at a surface speedof 15 meters per minute, and the upper set of nip rollers at a surfacespeed of 42 meters per minute. The result was 2.6× orientation in thetransverse direction and 3.0× orientation in the machine direction, fora total biaxial orientation of 7.8×. The resulting heat-shrinkable filmhad a total thickness of 3.9 mils. The table below provides values forvarious properties of the film of Example 1.

% free Film of shrink at Example 185° F. Transparency Haze Gloss No.(L + T) (%) (%) (%) 1 40 50.2 2.8 87

As can be seen in the table above, the film of Example 1 exhibited lowhaze and high transparency. In the film of Example 1, the percenttransparency was greater than or equal to 5.33 (% haze)−31.5.

Example 2

The film of Example 2 was prepared in a manner similar to thepreparation of the film of Example 1, described above. The film ofExample 2 also had a total of 7 layers, in the following order, with thethickness of each layer of the tape (i.e., prior to solid stateorientation) shown in mils being indicated below the layer identity andresin composition:

Example 2

Core Core 90% 90% Tie Nylon1 Nylon1 Tie Sealant MA- 10% Barrier 10% MA-Outer LLDPE3 LLD2 Nylon2 EVOH1 Nylon2 LLD2 LLDPE3 5 mils 1 mil 3 mils 1mil 3 mils 1 mil 5 mils

The process of making the film of Example 2 was generally as carried outfor the production of the film of Example 1. More particularly, thefollowing parameters were employed:

Die diameter 12.7 Cm Total extrudate thickness 19 mils Air shoe outsidediameter: 8 cm Air shoe length: 32 cm Temperature of air 15.6° C. Airshoe hole diameter 0.762 mm emitted from air shoe Distance between 14.3mm Position of Water Ring 57 mm below holes of air shoe die Watertemperature 7.2° C. Position of water 57 mm below emitted from waterring contact with extrudate die Hot bath temperature 83° C. immersiontime 2.5 seconds in hot bath distance between upper 1.9 meters surfacespeed of nip 15.8 m/min and lower nip rollers rollers below trappedbubble surface speed of nip rollers 51.8 m/min orientation factor 2.4 Xabove trapped bubble in machine direction orientation factor 3.3 X Totalbiaxial 7.9 X in transverse direction orientation Total thickness 2.3mils Number of 4 of heat-shrinkable film annealing rollers Diameter of 6inches Degree of wrap around 120 degrees annealing rollers eachannealing roller Surface temperature 57° C. Surface speed 51 m/min ofannealing rollers of annealing rollers

The film of Example 2 had a total thickness of 2.35 mils, exhibited aHaze of 23.6 percent, a Transparency of 5.8 percent, and a Gloss of 34percent, and a total free shrink at 185° F. of 34% in the longitudinaldirection (i.e., the machine direction) and 30% in the transversedirection. Although this film was quenched, reheated, and oriented in amanner similar to the production of the film of Example 1, it exhibitedrelatively poor optical properties because the outer film layers weremade from 100% LLDPE3, which had a density of 0.918 g/cm³. Therelatively high density of this outer layer polymer is believed to bethe reason for the poor optical characteristics exhibited by the film ofExample 2.

Example 3

The film of Example 3 was prepared in a manner similar to thepreparation of the film of Example 2, described above. The film ofExample 3 also had a total of 7 layers, in the following order, with thetarget thickness of each layer of the tape (i.e., the intended thicknessof each layer of the tape, using the process design setup) shown in milsbeing indicated below the layer identity and resin composition:

Example #3

Core Core 90% 90% Tie Nylon3 Nylon3 Tie Sealant MA- 10% Barrier 10% MA-Outer LLDPE2 LLD1 Nylon2 EVOH1 Nylon2 LLD1 LLDPE2 5 mils 1 mil 4 mils 1mil 4 mils 1 mil 5 mils

The heat-shrinkable film of Example 3 was produced at three targetgauges: 2.5 mil, 3.0 mil, and 3.5 mil. In the production of the film ofExample 3, parameters employed were as set forth in the parameters tablein Example 2, except as follows:

Total Extrudate Thickness 23 mils Hot Bath Temperature 76° C. SurfaceSpeed of Nip 12.8 m/min Surface Speed of Nip Rollers 36.6 m/min RollersBelow Trapped Above Trapped Bubble Bubble orientation factor 2.8 Xorientation factor 2.9 X in transverse direction in longitudinaldirection Total Biaxial Orientation 8.1 X Total thickness of heat- 3.3mils shrinkable film (i.e., one of the three films produced) Surfacespeed of annealing 34.4 m/min rollersWhile the haze and transparency of the heat-shrinkable films produced inExample 3 were not measured, the film appeared to exhibit low haze andhigh transparency, i.e., a haze low enough, and a transparency highenough, that the percent transparency would have measured as beinggreater than or equal to 5.33 (% haze)−31.5. However, the film wasallowed to relax and wrinkle over time without the haze and transparencybeing measured, with the wrinkling interfering with any attempt tomeasure these optical values.

Comparative Example 1

The film of Comparative Example 1 was prepared in a manner similar tothe preparation of the film of Examples 1-3, except that the film ofComparative Example 1 was prepared using and extrusion coating processas illustrated in FIG. 5, described above. The sealant layer, substratecore layer, and first tie layer were coextruded as a “substrate”, andthereafter irradiated, following which the barrier layer, second tielayer, coating core layer, and outer layers were extrusion coated ontothe substrate. The film of Comparative Example 1 also had a total of 7layers, in the following order, with the thickness of each layer of thetape (i.e., prior to solid state orientation) shown in mils beingindicated below the layer identity and resin composition:

Comparative Example 1

Sealant Substrate core Coating Core Outer 90% SSPE1 80% VLDPE2 TieBarrier Tie 80% VLDPE2 80% SSPE2 10% LLDPE2 20% VLDPE1 EVA1 PVdC EVA120% VLDPE1 20% LLDPE1 5 mils 14 mils 1 mil 2 mils 1 mil 3 mils 2 mils

In the preparation of the film of Comparative Example 1, the water ringwas located approximately 102 mm below the die, and the quenching watertemperature was 7.2° C. No air shoe was utilized below the die in thepreparation of the film of Comparative Example 1. Extremely rapidquenching of the extrudate emerging from the die was not needed becausethe film of Comparative Example 1 was ethylene-based, i.e., contained nocrystalline polyamide.

The quenched, partially-irradiated, extrusion coated tape was thenimmersed in a hot bath at a temperature of 93° C. for a period of 4seconds, following which the softened tape was biaxially oriented 3.4×in the machine direction and 3.6× in the transverse direction (totalorientation 12.2×) using the trapped bubble method. The resulting heatshrinkable film had a total thickness of 2.7 mils. As the film wasstable upon being wound onto a core, there was no need to anneal thefilm.

Comparative Example 2

The film of Comparative Example 2 was fully coextruded in a mannersimilar to the preparation of the film of Examples 1-3. However, thefilm of Comparative Example 2 was made using the water ring as inComparative Example 1, and no air shoe was used in the preparation ofComparative Example 2. The film of Comparative Example 2 also had atotal of 7 layers, in the following order, with the thickness of eachlayer of the tape (i.e., prior to solid state orientation) shown in milsbeing indicated below the layer identity and resin composition:

Comparative Example 2

Tie Tie Sealant Core MA- Barrier MA- Core Outer LLDPE3 VLDPE3 LLD2 EVOHLLD2 EVA2 VLDPE4 4 mils 5 mils 1 mil 1 mil 1 mil 6 mils 2 mils

In the preparation of the film of Comparative Example 2, the water ringwas located approximately 100 mm below the die, and the quenching watertemperature was 7.2° C. As with the film of Comparative Example 1, inthe process utilized to prepare the film of Comparative Example 2,extremely rapid quenching of the extrudate emerging from the die was notneeded because the film of Comparative Example 2 was ethylene-based,i.e., contained no crystalline polyamide.

The quenched coextruded tape was then immersed in a hot bath at atemperature of 95° C. for a period of 4 seconds, following which thesoftened tape was biaxially oriented 3.0× in the machine direction and3.3× in the transverse direction (total orientation 9.9×) using thetrapped bubble method. The resulting heat shrinkable film had a totalthickness of 2.3 mils. As the film was stable upon being wound onto acore, there was no need to anneal the film.

Comparative Example 3 Bag with Adhered Patch

The four layer bag film of Comparative Example 3 was produced using anextrusion coating process in a manner similar to the preparation of thefilm of Comparative Example 1. The sealant layer and the substrate corelayer were coextruded as the “substrate”, and thereafter irradiated,following which the barrier layer and abuse layer were coated thereonusing an extrusion coating die. As with the first two comparativeexamples above, the water ring was located approximately 100 mm belowthe die, and the quenching water temperature was 7.2° C., and no airshoe was used in the preparation of Comparative Example 2. The patch andbag films together had a total of 8 layers (or 9 layers, if each of thetwo 4 mil self-weld layers adhered to one another are considered to betwo layers rather than the one 8-mil layer listed in the table below),in the following order, with the thickness of each layer of the tape(i.e., prior to solid state orientation) shown in mils being indicatedbelow the layer identity and resin composition:

Comparative Example 3 Patch Bag with Bag Film Adhered to Patch Film(Film Layer Thicknesses Represent the Tape Thickness)

Bag Patch Patch Bag Film Adhesive Film Film Bag Film Bag Film Film OuterBetween Abuse and Patch film Abuse and Sealant Substrate Barrier Abusebag and Shrink Self Weld Shrink Layer core layer Layer Layer patch LayerLayer Layer VLDPE5 EVA4 PVdC EVA4 PU-A VLDPE5 EVA3 VLDPE5 3 mils 15 mils2 mils 7 mils 1 mils 22 mils 8 mils 22 mils

The quenched, partially irradiated, four-layer extrusion-coated bag filmtape was then immersed in a hot bath at a temperature of 92° C. for aperiod of 4 seconds, following which the softened tape was biaxiallyoriented 3.4× in the machine direction and 4.0× in the transversedirection (total orientation 13.6×) using the trapped bubble method. Theresulting heat shrinkable bag film had a total thickness of 2.4 mils. Asthe film was stable upon being wound onto a core, there was no need toanneal the film. This four-layer, extrusion coated, 2.4 mil,heat-shrinkable film was used to make an end-seal bag, to which amultilayer patch film was applied.

The multilayer heat-shrinkable patch film was prepared by fullycoextruding a two-layer, 50 mil thick, annular tape that was biaxiallyoriented (3.7× in the machine direction, 3.6× in the transversedirection) and thereafter self-welded to form a three layerheat-shrinkable patch film having a thickness of 4.5 mils. The tape wascomposed of outer abuse and shrink layers composed of 100% LLDPE4, andan inner self welded layer composed of 100% EVA3, as shown in the tableabove. The patch film was prepared using a process as illustrated inFIG. 1, except that the water ring was located approximately 10 mm belowthe die, and the quenching water temperature was 7.2° C.

Comparison of Film of Example 3 with Films of Comparative Examples 1-3

The film of Example 3 (at a total gauge of 2.5 mils, 3.0 mils, and 3.5mils), and the films of Comparative Examples 1, 2, and 3, were eachtested for impact strength, energy-to-break, and total free shrink at185° F. The results were as follows:

Total ITR Impact, Energy to Total Free Thickness (Newtons) Break Shrink(mils, target (ASTM (Joules) (L + T Film of thickness) D 3763) (ASTM D3763) at 185° F.) Example 3 2.5 432 5.5 62 Example 3 3.0 465 6.6 61Example 3 3.5 489 7.5 65 Comparative 2.7 390 6.7 60 Example 1Comparative 2.3 169 1.9 56 Example 2 Comparative 7.4 — — 32 Example 3(patch bag)

These results show the improvement in impact strength of the inventivematerials over comparable polyethylene-based films. While the patch baghad the highest impact strength, it was at least twice as thick as theother examples, and it did not exhibit the high shrink of thenylon-based films of Example 3.

End-seal bags were made from the three films made in accordance withExample 3, as set forth in the table above. Again, the first film had athickness of 2.5 mils, the second had a thickness of 3.0 mils, and athird film had a thickness of 3.5 mils. End-seal bags were also madeusing the films of Comparative Example 1, as well as a patch bag madeusing the patch-bag laminate of Comparative Example 3.

Fifty end-seal bags made from each film were tested by first loading thebags with nylon pellets and placed in a box and subjected to a shippingtest that was intended to simulate packaged product being shipped acrossthe United States in the trailer of a tractor trailer truck. Four hourson the testing apparatus was intended to simulate a twelve hour roadtrip, while eight hours is intended was intended to simulate a 24 hourtrip. In the final test, the force that was exerted on the boxes duringshaking was turned up from 0.2 Gs to 0.7 Gs in an effort to producefailures in the patch bag package utilizing the patch bag of ComparativeExample 3. The results obtained revealed that the packages made usingthe three films in accordance with Example 3 performed much better thanpackages made from the film of Comparative Example 1, and almost as wellas the packages made from the patch bags of Comparative Example 3.However, the 2.5, 3.0, and 3.5 mil films used in the test of the filmaccording to Example 3 had a thickness only about 50% of the total gaugeof the patch bag of Comparative Example 3 (i.e., 7.0 mils). Thefollowing test results were obtained from the bags:

Total Shipping Shipping Thickness Test Test (% (mils, target (% LeakersShipping Test Leakers thickness) 4 hrs) (% Leakers 8 hrs) .7G) Example 32.5 10 55 80 Example 3 3.0 5 30 70 Example 3 3.5 5 30 60 Comparative 2.795 100 100 Example 1 Comparative 7.0 0 0 50 Example 3 (patch bag)

Examples 4-25

Twenty-two different multilayer heat-shrinkable films were producedutilizing the apparatus and process set forth in FIG. 1, describedabove. The multilayer films each had a total of 7 layers, in thefollowing order, with the thickness of each layer of the tape (i.e.,prior to solid state orientation) shown in mils being indicated belowthe layer identity:

Nylon Core Nylon MA- (var- Core MA- VLDPE6 LLD1 iable) EVOH1 (variable)LLD1 VLDPE6 4 mils 1 mil 6 mils 1 mil 6 mils 1 mil 4 mils

Before solid-state orientation, the extrudate (i.e., tape) had athickness of about 23 mils and a lay-flat width of about 5 inches. Thetape for each of Examples 4-25 examples had the same actual and relativelayer thicknesses as set forth above. Moreover, the polymericcomposition of the outer layers, the tie layers, and the barrier layerwere kept the same in each of the films of Examples 4-25, and are asidentified in the resin table above.

The only compositional variation between the various films was thedifference in the composition of the two nylon core layers. For each ofthe films of Examples 4-25, the core layers were of identicalcomposition. However, each film had a different core layer composition,relative to the other films. Many of the nylon core layers in the filmsof Examples 4-25 contain a blend of a first polyamide present in adominant proportion with a secondary component in a subservientproportion. The secondary component is present for the purpose of“interrupting” the crystallinity of the dominant polyamide.

In the process, the extrudate emerged from the die with a diameter of 5inches. The process utilized an air shoe having a diameter of 3.26inches and a length of 16 inches. The upstream end of the air shoe waslocated approximately 2 inches downstream of the point at which theextrudate emerged from the die. The air inside the air shoe was at atemperature of 60° F. The air shoe had air passageway holes with adiameter of 0.762 mm, the holes being spaced apart by a distance of 14.3mm, the holes being in a pattern so that each interior hole wassurrounded by 6 holes spaced at an equal distance therefrom. The holeswere evenly distributed over the outer surface of the air shoe. The airshoe had an outer surface roughened with 80 grit sandpaper. Thisroughness lowered the friction in the event the extrudate came intocontact with the surface of the air shoe. The extrudate emerging fromthe die remained spaced from the surface of the air shoe due to the flowof air out of the air shoe. The airflow out of the air shoe passedbetween the extrudate and the air shoe, and thereafter passed downwardand then out through a pipe positioned through the center of the airshoe, the pipe allowing the air passing therethrough to pass through thedie stack and into the open atmosphere. The pressure around the outsideof the extrudate was ambient pressure.

A single water ring having an inside diameter of 102 mm was mounted 57mm below the point at which the extrudate emerged from the die. A streamof water emerged from the annular slit in the water ring, this slithaving a width of 2.0 millimeters. The water emitted from the water ringhad a temperature of 45° F. The annular stream of water emitted from thewater ring contacted the extrudate at a position 57 mm downstream of thepoint at which the extrudate emerged from the die.

Each of the tapes in Examples 4-25 was oriented by being immersed inwater at a temperature of 155° F. or 165° F. for a period of about 2seconds, depending upon the particular example. This heating step wascarried out immediately before the tape entered a set of nip rolls atthe base of a trapped bubble. The combination of the amount of air inthe trapped bubble of air, the length of the trapped bubble (dictated bythe distance between the upper lower nip rollers and the upper niprollers), and the difference in the surface speeds of the lower andupper nip rollers, was designed so that the heated tape underwent anorientation of 3.0× in the transverse direction and 2.25× in the machinedirection. The heated tape passed through the lower nip rollers at aspeed of approximately 65 feet per minute. The total orientation wasapproximately 6.75X×. While the thickness of the tape was about 23 mils,the thickness of the resulting solid-state oriented heat-shrinkable filmwas about 4 mils. The heat-shrinkable film was then annealed at atemperature of 135° F. or 145° F. (depending upon the example) for aperiod of about 2 seconds, by passing the film around 4 annealingrollers each having a diameter of 6 inches, with the oriented filmpassing about 120 degrees around each of the annealing rollers, at aspeed of about 120 feet per minute. The annealing step stabilized thefilm so that it could be wound up on a core without crushing the core,and so that the resulting roll was flat in appearance.

Table 1, below, provides the core layer composition for each of the 22films, as well as the percent total free shrink at 185° F. for each ofthe films, and comments regarding the appearance and processing of eachfilm.

Is % Total % Trans- Free parency ≧ Composition Shrink at 5.33 Film of ofthe Nylon 185° F. % Trans- (% Haze) − Ex. No. Core Layers (85° C.) %Haze parency 31.5? 4 90% Nylon 1 63 9.7 12.7 NO 10% Nylon 2 5 97% Nylon1 51 3.5 33.2 YES 3% Nylon 2 6 100% Nylon 1 DNA 8.7 16 YES 7 95% Nylon 1DNA DNA DNA DNA 5% Nylon 4 8 95% Nylon 1 69 15 7.9 NO* 5% EVOH 1 9 95%Nylon 1 69 17.2 1.6 NO* 5% EVOH 2 10 95% Nylon 1 63 14 6.3 NO* 5% Nylon5 11 95% Nylon 1 62 4.3 9 YES 5% Nylon 6 12 95% Nylon 1 60 DNA DNA DNA5% Nylon 3 13 95% Nylon 1 66 17 8.1 NO* 5% Nylon 7 14 95% Nylon 1 DNA 154.2 NO* 5% Nylon 18 15 95% Nylon 1 DNA 6.7 36.7 YES 5% Ionomer 16 95%Nylon 1 DNA DNA DNA NO** 5% EMA 1 17 95% Nylon 1 55 25.2 11.7 NO* 5%PETG 18 95% Nylon 1 DNA DNA DNA NO** 5% ELAS 1 19 95% Nylon 1 DNA DNADNA NO** 5% ELAS 2 20 95% Nylon 1 60 19.4 19.3 NO* 5% Nylon 8 21 95%Nylon 1 DNA DNA DNA DNA 5% PET 22 95% Nylon 1 DNA DNA DNA DNA 5% PBTYL23 95% Nylon 1 DNA DNA DNA NO** 5% SSPE 3 24 95% Nylon 1 DNA DNA DNANO** 5% LLDPE 1 25 100% Nylon 9 DNA DNA DNA NO** NO* = While thetransparency was measured as being not greater than or equal to 5.33 (%haze) − 31.5, the optical measurements were not accurate because thefilms samples were allowed to relax and become wrinkled, whichinterfered with the optical testing; testing on fresh, flat films wouldprovide accurate results which. The visual appearance of most, if notall of these samples,indicated that if the flat films were tested, theresults would have been that the % transparency would have been greaterthan or equal to 5.33 (% haze) − 31.5. NO** = A manual visual estimationmade that % transparency was less than 5.33 (% haze) − 31.5; haze andtransparency measurements not actually made;. DNA = data not available(visual appearance indicated that many, if not most or all of thesefilms, would exhibit a % transparency greater than or equal to 5.33 (%haze) − 31.5.While in general Film Nos. 4-25 exhibited good optical properties,including low haze and high transparency, data from optical analyses waseither not available or the was inaccurate because the films wereallowed to relax and wrinkle, making measurement of optical propertiesproduce inaccurate results.

Examples 26-33

The films of Examples 26-33, described below, were designed forpost-pasteurization end use. As used herein, the phrase“post-pasteurization” refers to the process of subjecting a packagedfood product to a temperature of from 200° F. to 211° F. for a period offrom 10 seconds to 10 minutes. Films designed for post-pasteurizationend use benefit from high abrasion resistance and high total free shrinkat 185° F.

The films of Examples 26, 27, and 29-33 are films containing relativelyhigh amounts of semi-crystalline polyamide, in contrast to the film ofExample 28 that is a polyethylene-based film. While the film of Example28 is crosslinked, the films of Examples 26 and 27 are non-crosslinked.The films of Examples 29-33 are additional films designed forpost-pasteurization end use.

Examples 26 and 27

The film of Example 26, and the film of Example 27, were multilayer,coextruded, non-crosslinked, heat-shrinkable, annular films producedutilizing the apparatus and process set forth in FIG. 1, describedabove. More particularly, the parameters employed in the process ofmaking the films of Examples 26 and 27 were the same as the parametersin the table accompanying Example 2, above. The films of Examples 26 and27 had a layer arrangement and polymeric composition set forth in thetables below.

Example 26

Core Core 90% 90% Tie Nylon1 Nylon1 Tie Sealant MA- 10% Barrier 10% MA-Outer VLDPE1 LLD2 Nylon2 EVOH Nylon2 LLD2 VLDPE1 5 mils 1 mil 3 mils 1mil 3 mils 1 mil 5 mils

Example 27

Tie Core Core Tie Sealant MA- 90% Nylon 1 Barrier 90% Nylon 1 MA- OuterLLDPE3 LLD 2 10% Nylon 2 EVOH 10% Nylon 2 LLD 2 LLDPE3 5 mils 1 mil 3mils 1 mil 3 mils 1 mil 5 mils

The film of comparative Example 28 was a multilayer, extrusion-coated,crosslinked, heat-shrinkable, annular film produced utilizing theapparatus and process set forth in FIG. 5, described above. Themultilayer film had a total of 7 layers, in the following order, withthe thickness of each layer of the tape (i.e., prior to solid stateorientation) shown in mils being indicated below the layer identity andresin composition identification:

Example 28 (Comparative)

Substrate Tie Tie Coating Sealant Core MA- Barrier MA- Core Outer LLDPE3VLDPE3 LLD 2 EVOH LLD 2 EVA2 VLDPE4 4 mils 5 mil 1 mil 1 mil 1 mil 6mils 2 mils

During post-pasteurization, packages containing various types of meatproducts can be subjected to different types of abuse. Packages canexperience movement through the process on conveyor rolls, belts, movingarms, slides, drops, etc. This processing can be carried out over a widevariety of temperatures, ranging from refrigerated temperatures up to210° F. (i.e., pasteurization temperature). Moreover, some types of meatproducts have an outer coating that is highly abusive, such aspeppercorns, deep fried oil, etc. These types of products, along withthe tortuous environment associated with post-pasteurization, oftenresult in package failure due to abrasion and/or puncture. Packageshaving a failure are typically reworked if discovered during inspection.Alternatively, leaking packages may be returned. Both reworking andpackage return produce significant cost increases. In the most severeapplications, it is necessary to double bag the product to ensurepackage integrity. Double bagging is highly undesirable because it addsto package costs and increases the amount of labor expended.

The films of Examples 26 and 27, as well as the film of comparativeExample 28, were used to package a product that was thereafter subjectedto test simulating a post-pasteurization process. Relative to theperformance of the films of Examples 26 and 27, the film of comparativeExample 28 was found to exhibit poor abrasion resistance during thepost-pasteurization process. The poor abrasion resistance of the film ofcomparative Example 28 was particularly apparent when the productpackaged was a meat product having a surface including hard granules,such as peppercorns. While the solution to this problem could have beento increase the gauge of the film of comparative Example 28, increasingthe gauge has an adverse effect upon sealability and cost. Moreover, itwas found that in the most abrasive environments, increasing the gaugefrom 2.35 to 3.0 mils did not correct the abrasion resistance problem.

A simulated Post-Pasteurization Test was conducted by converting each ofthe films of Examples 26, 27, and 28 to bags, and then filling the bagswith 1.5 pounds of resin pellets (length of 2 mm and diameter of 3 mm).The resin pellets were a mixture of 80% polyethylene and 20% polyamide6. Once the bags were filled, the atmosphere was evacuated from thebags, and the bags were closed by heat sealing. Each of the resultingpackages was placed into boiling water in a kettle, and agitated withpaddles at about 4 revolutions per minute. This test showed asignificantly less abrasion-induced leakers for the films of Examples 26and 27 versus the film of comparative Example 28. The films of Examples27 and 28 were also tested for impact strength. Data from the varioustests carried out was as follows:

Impact Strength: Post- Total Energy Gauge Pasteurization (ft-lb_(f))measured at Example No. (mils) Test (% leakers) 210° F. 80° F. 40° F. 262.35 10 DNA DNA DNA 27 2.35 16 6.0 3.5 2.6 28 2.35 90 0.6 1.7 1.9(comparative) DNA = data not available

It was found that the films of Examples 26 and 27 were much tougher thanthe film of comparative Example 28 on a per mil basis. It was alsodiscovered that the films of Examples 26 and 27 were much moreabrasion-resistant than the film of comparative Example 28, on a per milbasis. Moreover, while the film of Example 26 possessed excellent optics(haze of 3.3%, transparency of 26.8%), while the film of Example 27exhibited more haze and less transparency (haze of from 23.6%,transparency of 5.8%). The film of Example 27 exhibited an inferiorcombination of haze and transparency because it had an outer layer madefrom LLDPE 3, which had a density of 0.918 g/cm³. However, both filmsexhibited high total free shrink at 185° F. and high puncture strength.The superior abrasion-resistance of the films of Examples 26 and 27versus the film of comparative Example 28, decreased the need to reworkleaking bags by repackaging the product, and eliminated the need fordouble bagging. Thus, the process of the invention produced a film thatwas highly cost-effective, relative to the film of comparative Example28.

Examples 29-33

Five additional polyamide-containing multilayer heat-shrinkable filmswere made, each of these films having been designed specifically forpost-pasteurization end use. The tables below provide the layerarrangement, identity, and relative thickness for each of the tapes thatwere oriented to make heat-shrinkable post-pasteurization films for eachof Examples 29-33. The tapes that were oriented had a thickness of 11.5mils before solid-state orientation, with the resulting heat-shrinkablefilm having a total thickness of 2.35 mils after solid-stateorientation. Otherwise, the films of Examples 29-33 were prepared with aprocess similar to the process used for the preparation of Examples 26and 27.

Example 29

Core Core Sealant Tie 90% Nylon 1 Barrier 90% Nylon 1 Tie Outer VLDPE 6MA-LLD2 10% Nylon 2 EVOH 10% Nylon 2 MA-LLD2 VLDPE 6 1.4 mils 0.9 mil 3mils 0.9 mil 3 mils 0.9 mil 1.4 mils

Example 30

Core Core Sealant Tie 90% Nylon 1 Barrier 90% Nylon 1 Tie Outer VLDPE 6MA-LLD2 10% Nylon 5 EVOH 10% Nylon 5 MA-LLD2 VLDPE 6 1.4 mils 0.9 mil 3mils 0.9 mil 3 mils 0.9 mil 1.4 mils

Example 31

Core Core Sealant Tie 90% Nylon 1 Barrier 90% Nylon 1 Tie Outer VLDPE 6MA-LLD2 10% EVOH 2 EVOH 10% EVOH 2 MA-LLD2 VLDPE 6 1.4 mils 0.9 mil 3mils 0.9 mil 3 mils 0.9 mil 1.4 mils

Example 32

Core Core Sealant Tie 90% Nylon 1 Barrier 90% Nylon 1 Tie Outer VLDPE 6MA-LLD2 10% Nylon 10 EVOH 10% Nylon 10 MA-LLD2 VLDPE 6 1.4 mils 0.9 mil3 mils 0.9 mil 3 mils 0.9 mil 1.4 mils

Example 33

Core Core Sealant Tie 90% Nylon 1 Barrier 90% Nylon 1 Tie Outer VLDPE 6MA-LLD2 10% Nylon 11 EVOH 10% Nylon 11 MA-LLD2 VLDPE 6 1.4 mils 0.9 mil3 mils 0.9 mil 3 mils 0.9 mil 1.4 milsThe films of Examples 29-33 were subjected to a variety of tests, andcompared against the film of comparative Example 28. The films ofExamples 29-33 were evaluated and found to exhibit improved impactproperties over the film of comparative Example 28, at all temperatures.The film of Example 29 appeared to have slightly lower impact valuescompared to the films of Examples 30-33. In addition, unrestrained freeshrink was measured in accordance with ASTM D 2732. The tables belowprovide the unrestrained free shrink data for the films of Examples29-33. Unrestrained free shrink was measure at both 185° F. and 195° F.

Free Shrink at 185° F.

Film of Total Free Example Transverse Free Longitudinal Free Shrink atNo. Shrink at 185° F. (%) Shrink at 185° F. (%) 185° F. (%) 29 25 29 5430 22 21 43 31 20 23 43 32 25 22 47 33 20 23 43

Free Shrink at 195° F.

Film of Total Free Example Transverse Free Longitudinal Free Shrink atNo. Shrink at 195° F. (%) Shrink at 195° F. (%) 185° F. (%) 29 27 31 5830 26 22 48 31 20 26 46 32 26 24 50 33 23 24 47The shrink data above was not taken during production of the tubing.Rather, this shrink data was taken at least a week after tubingproduction. Shrink data measured during production was higher thanshrink data measured one week later.

The evaluation of the optical properties of the films of Examples 29-33was conducted, including measurement of haze, transparency (i.e.,clarity), and gloss. The results of the optical measurements were asfollows:

Optical Properties of Films of Examples 29-33

Film of Is Example % Transparency ≧ No. Haze (%) Clarity (%) Gloss (%)5.33(% Haze) − 31.5? 29 7.4 11.6 74 YES 30 5.6 18.8 76 YES 31 4.1 27.486 YES 32 5.3 27.7 79 YES 33 9.6 14.3 67 NOWhile the films of Examples 29-32 exhibited a combination of haze andtransparency such that % Transparency >5.33(% Haze)−31.5, the film ofExample 33 did not exhibit this combination of haze and transparency.The inferior combination of haze and transparency in the film of Example33 is believed to be due to the presence of a polyamide core layercontaining a high molecular weight polyamide MXD6 which was found to beoptically incompatible with the polyamide 6 with which it was blended.The result was an extrudate that appeared cloudy even before it wascontacted with the quenching liquid.

Evaluation of the oxygen transmission rate of films of Examples 29-33was also conducted, including measurement taken at 23° C. and 100%relative humidity, and measurements taken at 23° C. and 0% relativehumidity. Three measurements were taken for each film, in accordancewith ASTM D-3985, with the results averaged. The tables below set forththe results of the oxygen transmission rate testing. As used herein theterm “gas-barrier” when referred to a layer or to an overall structure,is used to identify layers or structures characterized by an OxygenTransmission Rate (evaluated at 23° C. and 0% R.H. according to ASTMD-3985) of less than 500 cm³/m².day.bar.

O₂-Transmission Rate (cc/m² Day Atm, at STP and 0% Relative Humidity)

Film of Example No. Test 1 Test 2 Test 3 AVG. 29 9.55 8.7 7.32 8.5 3010.79 10.09 11.1 10.7 31 6 6.86 6.33 6.4 32 7.65 7.64 7.79 7.7 33 8.48.9 8.92 8.7

O₂-Transmission Rate (cc/m² Day Atm, at STP and 100% Relative Humidity)

Film of Example No. Test 1 Test 2 Test 3 AVG. 29 6.72 6.88 6.04 6.5 308.37 7.82 5.08 7.1 31 5.4 5.14 5.74 5.4 32 5.02 6.3 5.91 5.7 33 6.73 5.97.11 6.6Evaluation of tear propagation (in accordance with ASTM D 1938) and tearresistance (in accordance with ASTM D 1004), were measured for each ofthe films of Examples 29-33. The tables below set forth the results ofthese tests.

Tear Propagation

Film of Longitudinal Direction: Transverse Direction: Example No. Loadat Maximum (gmf) Load at Maximum (gmf) 29 41.9 70.8 30 36.4 60.4 31 37.180.4 32 40.6 75.3 33 48 81.7

Tear Resistance

Film of Longitudinal Direction: Transverse Direction: Example No. Loadat Max. Load (gmf) Load at Max Load (gmf) 29 1060 1130 30 1160 1170 311200 1230 32 1300 1310 33 1200 1210

Impact strength testing was carried out on each of the films of Examples28-33, using a Dynatup impact strength testing device in a manner inaccordance with ASTM D 3763. Measurements were taken of maximum load inpounds for each of the films, these measurements being made at threedifferent temperatures: 40° F., at 80° F., and at 210° F. Measurementswere also taken of deflection at maximum load (in inches) for each film,again at 40° F., 80° F., and 210° F. Finally, measurements of totalenergy to break were taken for each film (in foot pounds force) for eachfilm, again at 40° F., 80° F., and 210° F. The tables below provide thedata for the Dynatup measurements.

Impact Strength of Films 28-33: Maximum Load Dynatup Measurements inAccordance with ASTM D 3763

Film of Example Max Load at Max Load at 80° F. Max Load at No. 40° F.(lb) (lb) 210° F. (lb) 28 13.9 43.6 49.3 29 45 58.1 61.1 30 50 72.8 57.931 51.9 69.6 63.3 32 48 71.7 64.7 33 49.7 62.4 60.5

Impact Strength of Films 28-33: Deflection at Maximum Load DynatupMeasurements in Accordance with ASTM D 3763

Deflection at Deflection at Deflection at Film of Example Max Load atMax Load at Max Load at No. 40° F. (in) 80° F. (in) 210° F. (in) 28 1.11.06 0.94 29 1.5 1.09 0.85 30 1.5 1.30 0.88 31 1.5 1.10 0.77 32 1.5 1.200.86 33 1.5 1.10 0.81

Total Energy to Total Energy to Total Energy to Film of Example Break at40° F. Break at 40° F. Break at 40° F. No. (ft-lbsf) (ft-lbsf) (ft-lbsf)28 0.7 1.7 1.7 29 5.3 2.7 2.3 30 5.8 3.8 2.4 31 6.0 3.3 2.1 32 5.5 3.82.5 33 5.8 3.0 2.1

Examples 34-41

The films of Examples 34-41 are heat-shrinkable, multilayer films foruse in packaging food products, particularly fresh meat products. Thebags are designed to possess high abuse properties for the packaging ofbone-in meat products, while at the same time possessing high total freeshrink at 185° F., low haze, high transparency, strong heat seals, andeasy sealability. While the bags could be provided with patches foradditional puncture resistance for the packaging of particularly abusivebone-in meat products, the bags are designed to be patchless forpackaging bone-in meat products of low to moderate abuse levels.

The films of Examples 34-41 were coextruded made using the process ofFIG. 1, described above. More particularly, the following parameterswere employed in the process of making the films of Examples 34-41:

Die diameter 12.7 cm Total extrudate thickness 25 mils Air shoe outsidediameter: 8 cm Air shoe length: 32 cm Temperature of air 15.6° C. Airshoe hole diameter 0.762 mm emitted from air shoe Distance between 14.3mm Position of Water Ring 57 mm below holes of air shoe die Watertemperature 7.2° C. Position of water 57 mm below Emitted from waterring contact with extrudate die Hot bath temperature 80° C. immersiontime 2.5 seconds in hot bath distance between upper 1.9 meters surfacespeed of nip 17.7 m/min and lower nip rollers rollers below trappedbubble surface speed of nip rollers 39.6 m/min orientation factor 2.3Xabove trapped bubble in machine direction (±10%) orientation factor 3.0XTotal biaxial 6.9X in transverse direction (±10%) orientation Totalthickness 4.0 mils Number of 4 Of heat-shrinkable film annealing rollersDiameter of 6 inches Degree of wrap around 120 degrees annealing rollerseach annealing roller Surface temperature 51 m/min Surface speed 50m/min Of annealing rollers of annealing rollersThe films of Examples 34-41 had the layer arrangements and polymericcompositions set forth in the tables below.

Example 34

Core Barrier Core Tie Outer Tie 90% 100% 90% 100% Outer 100% 100% Nylon1 EVOH Nylon 1 MA- 100% VLDPE 6 MA-LLD 1 10% Nylon 2 1 10% Nylon 2 LLD 1VLDPE 6 4 mils 1 mil 6 mils 1 mil 6 mils 1 mil 4 mils

Example 35

Tie Core Core Tie Outer 100% 90% Barrier 90% 100% Outer 100% MA- Nylon 1100% Nylon 1 MA- 100% VLDPE 6 LLD 1 10% EVOH 2 EVOH 1 10% EVOH 2 LLD 1VLDPE 6 4 mils 1 mil 6 mils 1 mil 6 mils 1 mil 4 mils

Example 36

Tie Core Core Tie Outer 100% 90% Barrier 90% 100% Outer 100% MA- Nylon 1100% Nylon 1 MA- 100% VLDPE 6 LLD 1 10% Nylon 5 EVOH 1 10% Nylon 5 LLD 1VLDPE 6 4 mils 1 mil 6 mils 1 mil 6 mils 1 mil 4 mils

Example 37

Tie Core Core Tie Outer 100% 90% Barrier 90% 100% Outer 100% MA- Nylon 1100% Nylon 1 MA- 100% VLDPE 6 LLD 1 10% Nylon 3 EVOH 1 10% Nylon 3 LLD 1VLDPE 6 4 mils 1 mil 6 mils 1 mil 6 mils 1 mil 4 mils

Example 38

Tie Core Core Tie Outer 100% 90% Barrier 90% 100% Outer 100% MA- Nylon 1100% Nylon 1 MA- 100% VLDPE 6 LLD 1 10% Nylon 7 EVOH 1 10% Nylon 7 LLD 1VLDPE 6 4 mils 1 mil 6 mills 1 mil 6 mils 1 mil 4 mils

Example 39

Tie Core Core Tie Outer 100% 90% Barrier 90% 100% Outer 100% MA- Nylon 1100% Nylon 1 MA- 100% VLDPE 6 LLD 1 10% Nylon 4 EVOH 1 10% Nylon 4 LLD 1VLDPE 6 4 mils 1 mil 6 mils 1 mil 6 mils 1 mil 4 mils

Example 40

Tie Core Core Tie Outer 100% 90% Barrier 90% 100% Outer 100% MA- Nylon 3100% Nylon 3 MA- 100% VLDPE 6 LLD 1 10% Nylon 5 EVOH 1 10% Nylon 5 LLD 1VLDPE 6 4 mils 1 mil 6 mils 1 mil 6 mils 1 mil 4 mils

Example 41

Tie Tie Outer 100% Core Barrier Core 100% Outer 100% MA- 100% 100% 100%MA- 100% VLDPE 6 LLD 1 Nylon 1 EVOH 1 Nylon 1 LLD 1 VLDPE 6 4 mils 1 mil6 mils 1 mil 6 mils 1 mil 4 mils

The films of Examples 46-54, 56, and 57 were analyzed for variousoptical properties, with results provided in the table below.

Is Film of % Transparency ≧ Example % % % Gauge 5.33(% Haze) − No. HazeTransparency Gloss (mils) 31.5? 34 4.2 22.6 79 4.6 YES 35 5.1 42.5 844.12 YES 36 5.5 37.2 82 4.13 YES 37 8.1 9.1 68 4.38 NO 38 4.8 32.4 803.57 YES 39 4.7 29.6 86 4.26 YES 40 7.1 17 73 4.01 YES 41 8.3 23.2 714.08 YES

The film of Example 37 exhibited an inferior combination of opticalproperties, compared with superior optical properties exhibited by thefilms of Examples 34-36, 38, 39, 40, and 41. The inferior opticalproperties for the film of Example 37 is believed to be due to thepresence of a high molecular weight Nylon 3 (Ultramid® B 50 polyamide 6)which is believed to be produce inferior optical characteristics in thefilm when blended at the 10% level with 90% Nylon 1 (Ultramid® B40polyamide 6).

The films of Examples 34-36, 38, 39, 40, and 41 exhibited relatively lowhaze and relatively high clarity (i.e., high transparency), i.e.,relative to commercially-available polyamide-based shrink films producedusing the process and equipment developed by Kuhne Anlagenbau GMBH. Thetable below provides optical results for several commercially availablefilms offered by Vector Packaging, Inc. and Pechiney Plastic Packaging,these films believed to be produced using the process developed by KuhneAnlagenbau GMBH.

Film of % % % Is % Transparency ≧ Example No. Haze Transparency Gloss5.33(% Haze) − 31.5? Vector 8.2 11.1 78 NO Sample No. 1 Vector 15.1 47.764 NO Sample No. 2 Vector 16.1 51.2 61 NO Sample No. 3 Vector 13.5 11.855 NO Sample No. 4 Vector 19.7 DNA 59 DNA Sample No. 5 Vector 18.8 27.951 NO Sample No. 6 Vector 16.7 40.9 52 NO Sample No. 7 Pechiney 11.1 667 NO Sample No. 1 Pechiney 11.2 12.5 60 NO Sample No. 2 Pechiney 15.44.3 56 NO Sample No. 3 Pechiney 7.8 7.7 72 NO Sample No. 4 Pechiney 11.29.7 73 NO Sample No. 5 Pechiney 10.9 5.8 67 NO Sample No. 6 Pechiney 1013.7 72 NO Sample No. 7 Pechiney 9.7 8.7 70 NO Sample No. 8 Pechiney11.5 14.1 70 NO Sample No. 9 Pechiney 11 10 70 NO Sample No. 10 DNA =data not available

A comparison of the haze and transparency for the films of Examples34-39, 40, and 41 with the haze and transparency of the films of VectorPackaging, Inc. and the films of Pechiney Plastic Packaging, revealsthat the films of Examples 34-36, 38, 39, 40, and 41 exhibit ameasurably superior combination of low haze and high transparency. Moreparticularly, FIG. 10 illustrates, in graphical format, the dataprovided in the two tables above, as well as a line representing theequation:

% Transparency=5.33 (% Haze)−31.5

In FIG. 10, all of the points above and to the left of the linerepresenting this equation are films in accordance with the presentinvention. In stark contrast, all of the above-described polyamide-basedshrink films from Vector Packaging, Inc., and Pechiney PlasticPackaging, exhibited a combination of haze and transparency below and tothe right side of the line represented by the equation above. Thus, thefilms of Examples 34-36, 38, 39, 40, and 41 satisfy the equation:

% Transparency>5.33 (% Haze)−31.5.

However, as set forth in the table above, none of the commerciallyavailable films tested from Vector Packaging, Inc., or Pechiney PlasticPackaging, satisfied this equation.

Examples 42-55 Barrier Shrink Films Containing Polyvinylidene Chloride

The heat-shrinkable multilayer films of Examples 42-55 were made usingthe extrusion coating process illustrated in FIG. 5, described above.However, no portion of the tape or final film was irradiated. Each ofthe films had a target final thickness of about 4 mils and a target tapethickness of about 23 mils. More particularly, the following parameterswere employed in the process of making the films of Examples 42-55:

Die diameter 12.7 cm Air shoe outside diameter: 7 cm Air shoe length: 40cm Temperature of air 15.6° C. Air shoe hole diameter 0.762 mm emittedfrom air shoe Distance between 19 mm Position of Water Ring 51 mm belowholes of air shoe Below extrusion die extrusion die Water temperature7.2° C. Position of water 51 mm below emitted from water ring contactwith extrudate below extrusion die below extrusion die extrusion diePosition of Water Ring 200 mm Water temperature 7.2° C. Below extrusioncoating below emitted from water ring below die extrusion extrusioncoating die coating die Position of water 200 mm Hot bath temperature65–71° C. contact below extrusion below coating die extrusion coatingdie immersion time 2.5 seconds distance between upper 1.9 meters in hotbath and lower nip rollers surface speed of nip 14.6–18.3 m/min surfacespeed of nip rollers 33.6–42.1 m/min rollers below trapped above trappedbubble bubble orientation factor 2.3X orientation factor 2.4X in machinedirection (±10%) in transverse direction (±10%) Total biaxial 5.5X Filmwas not annealed orientation

The films of Examples 42-55 had the layer arrangements and polymericcompositions set forth in the tables below.

Example 42

Outer Tie Core Tie Barrier Tie Core Outer 100% 100% 90% Nylon 1 100%100% 100% 100% 100% VLDPE 6 MA-EVA 1 10% Nylon 2 MA-EVA 1 PVdC EVA 4VLDPE 6 VLDPE 6 6.2 mils 0.9 mil 7.4 mils 1.9 mils 2.2 mils 1.2 mils 2.5mils 0.9 mil

Example 43

Tie Core Tie Outer Outer 100% 90% 100% Barrier Tie 100% 100% MA- Nylon 1EMA 100% 100% VLDPE VLDPE 6 EMA 2 10% Nylon 2 MA- PVdC EVA 4 6 5.4 mils0.9 mil 9.7 mils 1.5 mils 1.9 mils 1.2 mil 2.3 mils

Example 44

Tie Core Tie Outer Outer 100% 90% 100% Barrier Tie 100% 100% MA- Nylon 1EMA 100% 100% VLDPE VLDPE 6 EMA 10% Nylon 2 MA- PVdC EVA 4 6 4.3 mils0.7 mil 10.1 mils 1.3 mils 1.8 mils 1.6 mil 3.3 mils

Example 45

Tie Tie Outer 100% Core 100% Barrier Tie Outer 100% MA- 100% MA- 100%100% 100% VLDPE 6 EVA 1 Nylon 1 EVA 1 PVdC EVA 4 VLDPE 6 4.5 mils 0.5mil 10.8 mils 1.3 mils 1.5 mils 1.3 mils 3.1 mils

Example 46

Outer Tie Core Tie Barrier Tie Core Outer 100% 100% 90% Nylon1 100% 100%100% 100% 100% VLDPE 6 MA-EVA 1 10% EVOH 2 MA-EVA 1 PVdC EVA 4 VLDPE 6VLDPE 6 5.4 mils 0.5 mil 9.4 mills 1.3 mils 1.8 mils 1.2 mils 3.2 mils0.3 mil

Example 47

Outer Tie Core Tie Barrier Tie Core Outer 100% 100% 90% Nylon1 100% 100%100% 100% 100% VLDPE 6 MA-EVA 1 10% Nylon 10 MA-EVA 1 PVdC EVA 4 VLDPE 6VLDPE 6 5.0 mils 0.4 mil 10.4 mils 1.1 mils 1.7 mils 1.3 mils 2.7 mils0.3 mil

Example 48

Outer Tie Core Tie Barrier Tie Core Outer 100% 100% 80% Nylon 1 100%100% 100% 100% 100% VLDPE 6 MA-EVA 1 20% Nylon 16 MA-EVA 1 PVdC EVA 4VLDPE 6 VLDPE 6 5.0 mils 0.5 mil 9.8 mils 1.3 mil 1.8 mils 1.3 mils 3.0mils 0.3 mil

Example 49

Outer Tie Core Tie Barrier Tie Core Outer 100% 100% 100% 100% 100% 100%100% 100% LMDPE 1 MA-EVA 1 Nylon 1 MA-EVA 1 PVdC EVA 4 VLDPE 6 VLDPE 6 3mils* 1 mil* 12 mils* 1 mil* 2 mils* 1 mil* 2 mils* 1 mil* *= targetthickness; actual thickness not measured

Example 50

Outer Tie Core Tie Barrier Tie Core Outer 100% 80% MA-EVA 1 90% Nylon 180% MA-EVA 1 100% 100% 100% 100% VLDPE 6 20% SSPE 4 10% EVOH 2 20% SSPE4 PVdC EVA 4 VLDPE 6 VLDPE 6 4.8 mils 0.6 mil 10.2 mils 1.5 mils 1.7mils 1.1 mils 2.7 mils 0.3 mil

Example 51

Outer Tie Core Tie Barrier Tie Core Outer 100% 100% 90% Nylon 17 100%100% 100% 100% 100% VLDPE 6 MA-EVA 1 10% EVOH 2 MA-EVA 1 PVdC EVA 4VLDPE 6 VLDPE 6 3 mils* 1 mil* 12 mils* 1 mil* 2 mils* 1 mil* 2 mils* 1mil* *= target thickness; actual thickness not measured

Example 52

Tie Core Tie Outer Outer 100% 90% Nylon 3 100% Barrier Tie 100% 100% MA-10% MA- 100% 100% VLDPE VLDPE 6 EVA 1 EVOH 2 EVA 1 PVdC EVA 4 6 6.6mills 0.3 mil 9.6 mils 1.4 mils 1.4 mils 1.1 mils 2.6 mils

Example 53

Outer Tie Core Tie Barrier Tie Core Outer 100% 100% 90% Nylon 1 100%100% 100% 100% 100% VLDPE 6 MA-LLD 2 10% EVOH 2 MA-LLD 2 PVdC EVA 4VLDPE 6 VLDPE 6 3 mils* 1 mil* 12 mils* 1 mil* 2 mils* 1 mil* 2 mils* 1mil* *= target thickness; actual thickness not measured

Example 54

Outer Outer 100% Tie Core Tie Barrier Tie 100% VLDPE 100% 90% Nylon 1100% 100% 100% VLDPE 6 EVA 5 10% EVOH 2 EVA 5 PVdC EVA 4 6 4.8 mils 0.4mil 11.7 mils 1.0 mil 1.5 mils 1.0 mil 2.5 mils

Example 55

Tie Core 90% Tie Outer 100% Nylon 12 100% Barrier Tie Core Outer 100%MA- 10% MA- 100% 100% 100% 100% VLDPE 6 EVA 1 EVOH 2 EVA 1 PVdC EVA 4VLDPE 6 VLDPE 6 3 mils* 1 mil* 12 mils* 1 mil* 2 mils* 1 mil* 2 mils* 1mil* *= target thickness; actual thickness not measured

Optical Data for Films of Examples 42-52

Is % Trans- Example Haze** Transparency** Gloss 5.33(% haze) − parencyNo. (%) (%) (%) 31.5 higher? 28 7.5 12.5 73  8% Yes 43 15.4 4.4 54 51%No 44 19.4 3.7 40 72% No 45 32.5 2.5 47 142%  No 46 8.8 10.4 68 15% No47 11.8 9.5 63 31% No 48 8.6 8.2 68 14% No 50 11.7 7.7 62 31% No 52 7.022.3 73  6% Yes **Optics for many examples were poor due to airentrapment during extrusion-coating process. However, it is believedthat if the air entrapment had been avoided, the percent Transparencywould have been higher than 5.33(percent Haze) − 31.5.

Examples 56-60 Heat-Shrinkable Polyamide-Based Patch Films

The films of Examples 56-60 are heat-shrinkable, multilayer filmsdesigned for use as patch films, i.e., to be adhered to a bag film forthe preparation of a patch bag for the packaging of bone-in meatproducts and other high abuse products. While the patch film can have abarrier layer, it need not have a barrier layer. The films of Examples56-60 were prepared using the process according to FIG. 1, describedabove. More particularly, the following parameters were employed in theprocess of making the films of Examples 56-60:

Die diameter 12.7 cm Total extrudate thickness 13.5 mils Air shoeoutside diameter: 8 cm Air shoe length: 32 cm Temperature of air 15.6°C. Air shoe hole diameter 0.762 mm emitted from air shoe Distancebetween 14.3 mm Position of Water Ring 57 mm below holes of air shoe dieWater temperature 7.2° C. Position of water 57 mm below emitted fromwater ring contact with extrudate die Hot bath temperature 71° C.immersion time 2 seconds in hot bath distance between upper 1.9 meterssurface speed of nip 18.3 m/min and lower nip rollers rollers belowtrapped bubble surface speed of nip rollers 38.4 m/min orientationfactor 2.1X above trapped bubble in machine direction orientation factor2.8X Total biaxial 5.88X in transverse direction orientation Totalthickness 2.8 mils Number of 4 of heat-shrinkable film annealing rollersDiameter of 6 inches Degree of wrap around 120 degrees annealing rollerseach annealin roller Surface temperature 54° C. Film tension 6803 gramsof annealing rollers over annealing rollersThe following tables provide the layer arrangement, layer composition,relative layer thicknesses, total tape thickness, final film thickness(after annealing), and total free shrink.

Example 56 (13.5 mil Tape)

Core Core Tie 90% 90% Tie Outer 100% Nylon 1 Barrier Nylon 1 100% Outer100% MA- 10% 100% 10% MA- 100% VLDPE 6 LLD 2 Nylon 2 EVOH 1 Nylon 2 LLD2 VLDPE 6 17% 4.5% 26% 5% 26% 4.5% 17% Total tape thickness: Final FilmTotal Free Shrink @ 13.5 mils Thickness: 3.2 mils 185° F.: 65%

Example 57 (13.5 mil Tape)

Core Core Tie 90% 90% Tie Outer 100% Nylon 1 Tie Nylon 1 100% Outer 100%MA- 10% 100% 10% MA- 100% VLDPE 6 LLD 2 Nylon 2 MA-LLD2 Nylon 2 LLD 2VLDPE 6 17% 4.5% 26% 5% 26% 4.5% 17% Total tape thickness: Final FilmTotal Free Shrink @ 13.5 mils Thickness: 2.8 mils 185° F.: 60%

Example 58 (9.0 mil Tape)

Core Core Tie 90% 90% Tie Outer 100% Nylon 1 Tie Nylon 1 100% Outer 100%MA- 10% 100% 10% MA- 100% VLDPE 6 LLD 2 Nylon 2 MA-LLD2 Nylon 2 LLD 2VLDPE 6 17% 4.5% 26% 5% 26% 4.5% 17% Total tape thickness: Final FilmTotal Free Shrink @ 9.0 mils Thickness: 2.0 mils 185° F.: 70%

Example 59 (9.0 mil Tape)

Core Core Tie 90% 90% Tie Outer 100% Nylon 1 Tie Nylon 1 100% Outer 100%MA- 10% 100% 10% MA- 100% VLDPE 6 LLD 2 Nylon 2 MA-LLD2 Nylon 2 LLD 2VLDPE 6 12% 4.5% 31% 5% 31% 4.5% 12% Total tape thickness: Final FilmTotal Free Shrink @ 9.0 mils Thickness: 2.0 mils 185° F.: 98%

Example 60 (4.5 mil Tape)

Core Core Tie 90% 90% Tie Outer 100% Nylon 1 Tie Nylon 1 100% Outer 100%MA- 10% 100% 10% MA- 100% VLDPE 6 LLD 2 Nylon 2 MA-LLD2 Nylon 2 LLD 2VLDPE 6 5% 4.5% 38% 5% 38% 4.5% 5% Tape thickness: 4.5 mils Final Filmthickness: 1.0 mils

The films of Examples 56-60 appeared to exhibit relatively low haze andrelatively high transparency. However, no data is currently availablefor the haze and transparency of the films of Examples 56, 58, 59, and60. However, the film of Example 57 exhibited a haze of 3.8% and atransparency of 17.8%, i.e., in the film of Example 57, percenttransparency was greater than 5.33(% Haze)−31.5. Since the visualappearance of the films of Examples 56-60 was similar, it is believedthat each of the films of Examples 56-60, percent transparency wasgreater than 5.33(% Haze)−31.5.

Ovenable Films

Several heat-shrinkable, multilayer, ovenable films were designed andproduced for packaging a food product which could be cooked or reheatedin an oven while remaining surrounded by the film. While a monolayerfilm can serve as an ovenable film, the ovenable films in the examplesthat follow were designed as multilayer films in order to provide a seallayer having a lower melting point than at least one other layer of thefilm, for good sealability and for ease of converting the films intobags. The films were 100% polyamide, and exhibited low haze and hightransparency, making the films suitable for packaging food products,such as meats, for presentation in a retail case, etc. Thepolyamide-based heat-shrinkable films could also withstand a largeamount of abuse, e.g., so that a packaged product could survivedistribution across long distances. The films possessed the necessarytemperature resistance to survive cooking in an oven for several hours.

Examples 61-68

The films of Examples 61-68 provided a combination of puncture strengthand ovenability that made these films suitable for: (a) packaging ofmeat at a packing plant, (b) transporting the packaged meat to a retailstore followed by being placed in a retail case, and (c) purchase by aconsumer who then cooks the product in an oven while the product remainsin the same package. Such packages eliminate several reprocessing steps,each of which would otherwise add cost and increase the chance ofproduct contamination.

Each of the films of Examples 61-68 had a seal layer, a skin layer, anda core layer. Typically, the seal layer contained a polyamide having alower melting point than various polyamides in the remainder of thefilm. While the polyamide in the seal layer may have a high meltingpoint, preferably it melts before the polyamide in the core layer and/orthe polyamide in the skin layer (i.e., the layer which is to serve asthe outer layer of the package), in order to improve the sealability ofthe film.

The polyamide in the core layer may (optionally) provide the film withhigher barrier properties. Polyamides providing higher barrierproperties include, but are not limited to, amorphous polyamide and/orMXD6 polyamide. The various film layers can be modified in order toalter the surface properties and make the film easier to convert into abag or other packaging article by the addition of a slip agent orantiblock particles. In addition, any or all of the layers may bemodified to provide for enhanced stabilization to prevent color changeduring cooking and for improved stability to prevent the film frombecoming brittle or otherwise decreasing the integrity of the film.

The coextruded, multilayer, all-polyamide, heat-shrinkable, ovenablefilm of Example 61 was produced using the process of FIG. 1, describedabove. The film of Example 61 was prepared in a manner similar to thepreparation of the film of Example 1, described above. In the productionof the film of Example 61, parameters employed were as set forth inExample 1, except as follows:

Total Extrudate 18 mils Air shoe outside 10.2 cm Thickness diameter:Surface Speed of Nip 9.1 m/min Surface Speed of Nip 27.4 m/ Rollers minRollers Below Trapped Above Trapped Bubble Bubble orientation factor2.0X orientation factor 3.1X in transverse direction in longitudinaldirection Total Biaxial 6.2X Total thickness of heat- 3.5 milsOrientation shrinkable film Hot Bath Temperature 60° C.The film of Example 61 had a layer arrangement and polymeric compositionset forth in the table below.

Seal Outer 86% Nylon 12 Core 60% Nylon 14 10% Nylon 13 60% Nylon 14 28%Nylon 15 1% STBL 1 30% Nylon 15 10% Nylon 13 3% AB&S 10% Nylon 13 2%AB&S 6 mils 6 mils 6 milsThe resulting 3.5 mil heat-shrinkable film possessed good shrink (atotal free shrink at 185° F. of 59 percent), high puncture strength,good optical properties, and withstood four hours in the oven at 350° F.without degradation, embrittlement, or loss of package integrity.

The films of Examples 62-68 were made in accordance with the processused to make the film of Example 2, except that the polymericcomposition of the various layers were altered in accordance with thetables provided below. In addition, the absolute thicknesses andrelative thicknesses of the various film layers varied as noted in thetables below. In the production of the film of Example 62, parametersemployed were as set forth in Example 2, except as follows:

Total Extrudate Thickness 10 mils Air shoe outside diameter: 12.7 cmSurface Speed of Nip 23.2 m/min Surface Speed of Nip Rollers 59.5 m/minRollers Below Trapped Above Trapped Bubble Bubble orientation factor2.1X orientation factor 2.6X in transverse direction in longitudinaldirection Total Biaxial Orientation 5.4X Total thickness of heat- 2.0mils shrinkable film Hot Bath Temperature 71.1° C.The films of Examples 62-68 had a layer arrangement and polymericcomposition set forth in the tables below.

Example 62

Sealant Outer 87% Nylon 12 Core Core Core 89% Nylon 1 10% Nylon 13 90%Nylon 1 90% Nylon 1 90% Nylon 1 10% 2% SLIP 10% Nylon 10% Nylon 10%Nylon 13 1% STBL 1 13 13 Nylon 13 1% SLIP 2.5 mils 5.5 mils 2 milsIn the production of the film of Example 63, parameters employed were asset forth in Example 62, except as follows:

Total Extrudate Thickness 10 mils Air shoe outside diameter: 12.7 cmSurface Speed of Nip 18.9 m/min Surface Speed of Nip Rollers 49.4 m/minRollers Below Trapped Above Trapped Bubble Bubble orientation factor 1.9X orientation factor 2.7 X in transverse direction in longitudinaldirection Total Biaxial Orientation 5.1 X Total thickness of heat- 2.0mils shrinkable film Hot Bath Temperature 79.4° C.

The film of Example 63 had a layer arrangement and polymeric compositionset forth in the tables below.

Example 63

Sealant 87% Nylon 12 Core Core Outer 10% Nylon 13 90% Nylon 1 100% Core89% Nylon 1 2% SLIP 10% Nylon Nylon 90% Nylon 1 10% Nylon 13 1% STBL 113 13 10% Nylon 13 1% SLIP 2.5 mils 2 mils 1 mil 2.5 mils 2 mils

The film of Example 64 had a layer arrangement and polymeric compositionset forth in the tables below.

Example 64

Sealant 87% Nylon 12 Core Core Core Outer 10% Nylon 2 89% Nylon 1 89%Nylon 1 89% Nylon 1 89% Nylon 1 1% STBL 1 10% Nylon 2 10% Nylon 2 10%Nylon 2 10% Nylon 2 2% AB&S 1% STBL 1 1% STBL 1 1% STBL 1 1% STBL 1 2.1mils 5.8 mils 0.6 milsMoreover, unless noted otherwise, the parameters employed in the processof making the films of Example 64, as well as the films of Examples65-68 were as set forth in Example 2, except as noted otherwise in thetable below. In addition, the annealing rollers operated with a surfacetemperature of 54.4° C.

Surface Surface Surface speed speed speed Total Air of Nip of nip of HotMD TD Biax Total Shoe below above anneal bath Stretch Stretch Orientfree Example OD bubble bubble rollers temp Factor Factor Factor shrink @No (cm) (m/min) (m/min) (m/min) (° C.) (X) (X) (X) 185 F. 64 12.7 27.451.4 49.2 65.6 2.25 2.1 4.7 84 65 12.7 24.5 41.9 38.0 63.9 2.05 2.3 4.731 66 12.7 23.9 47.0 43.2 65.6 2.2 2.3 5.0 DNA 67 10.2 22.9 51.1 46.566.7 2.5 1.9 4.7 50 68 10.2 27.3 56.1 54.0 73.9 2.3 1.9 4.3 59

The films of Examples 65-68 had a layer arrangements and polymericcompositions as set forth in the table below.

Example 65

Sealant 87% Nylon 12 Core Core Outer 10% Nylon 2 89% Nylon 1 Core 89%Nylon 1 89% Nylon 1 1% STBL 1 10% Nylon 2 100% 10% Nylon 2 10% Nylon 22% AB&S 1% STBL 1 Nylon 2 1% STBL 1 1% STBL 1 2.5 mils 2 mils 1 mil 2.5mils 2 mils

Example 66

Sealant 67% Nylon 1 Core Core Core Outer 30% Nylon 2 89% Nylon 1 89%Nylon 1 89% Nylon 1 89% Nylon 1 1% STBL 1 10% Nylon 2 10% Nylon 2 10%Nylon 2 10% Nylon 2 2% AB&S 1% STBL 1 1% STBL 1 1% STBL 1 1% STBL 1 2.5mils 5.5 mils 2 mils

Example 67

Core Core Core Outer Sealant 89% Nylon 1 89% Nylon 1 89% Nylon 1 89%Nylon 1 97% Nylon 12 10% Nylon 10% Nylon 10% Nylon 10% Nylon 1% STBL 110 10 10 10 2% AB&S 1% STBL 1 1% STBL 1 1% STBL 1 1% STBL 1 2.5 mils 5.5mils 2 mils

Example 68

Sealant Core Core Outer 97% Nylon 89% Nylon 1 Core 89% Nylon 1 89% Nylon1 12 10% 89% Nylon 1 10% 10% 1% STBL 1 Nylon 10 10% Nylon 10 Nylon 10Nylon 10 2% AB&S 1% STBL 1 1% STBL 1 1% STBL 1 1% STBL 1 2.5 5.5 mils 2mils mils

Example 69

A coextruded multilayer heat-shrinkable retortable film is producedutilizing the apparatus and process set forth in FIG. 1, describedabove. The multilayer film has a total of 7 layers, in the followingorder, with the thickness of each layer of the tape (i.e., the extrudateprior to solid state orientation) shown in mils being indicated belowthe layer identity and resin composition identification:

Layer Arrangement, Composition, and Thickness of Film of Outer ExampleHigh 69 Sealant melt High melt Barrier point point Tie Core Barrier CoreTie poly- polymer Tie 1 Nylon 1 1 Nylon 1 Tie 1 mer 1.5 mils 1 mil 3.25mils 1 mil 3.25 mils 1 mil 1.5 milsThe identity of the various resins in the film of Example 66 is asfollows:

Resin code Resin Identity High Melting MDPE, HDPE, PEC, PA copolymer, PPHomopolymer Point Polymer Tie 1 Anhydride grafted LLDPE, MDPE, HDPE, PP,EVA, EMA, PEC Nylon 1 Semi-crystalline Nylon, Amorphous Nylon Barrier 1EVOH, Retortable EVOH, Amorphous Nylon, MXD6, MXD6/MXDI, andnanocomposite barrier materialsThe extrudate is cast from an annular die (diameter of 12.7 cm) over anair shoe that provides the melt with the needed support to minimizegauge band variation. The air shoe has an outside diameter of 12.7 cmand a length of 32 cm, and emits cool air (15.6° C.) through 0.762 mmdiameter holes spaced over the cylindrical surface of the air shoe, theholes being spaced apart by a distance of 14.3 mm, with the holes beingarranged so that each hole inside the matrix of holes were surrounded by6 holes. The airflow through the holes supports the film (so that itdoes not collapse) and cooled the film from the inside out, i.e., toassist in quenching the molten extrudate quickly to minimizecrystallization. The pressure between the air shoe and the film isslightly above atmospheric pressure (i.e., about 780 mm Hg). The coolair is pumped into the hollow air shoe and out the holes, with the airthen flowing down beneath the air shoe and then up out through apassageway through the center of the air shoe.

Although the air shoe assists in freezing the nylon to minimize crystalformation, most of the heat in the extrudate is removed using a waterring positioned approximately 2 inches below the annular die. The waterring emits a stream of cool water (e.g., at 7.2° C.) against the outersurface of the extrudate to produce sudden freezing of the extrudate tominimize crystallization in the nylon layers. The stream of cool watercontacts the extrudate at a distance of about 2 inches downstream of theannular die. The resulting quenched tape is collapsed into lay-flatconfiguration and wound up onto a reel and transported to equipment forsolid state orientation of the tape. The tape is then unwound andforwarded to a bath containing hot water, collapsed into lay-flatconfiguration, and heated to a temperature of 71° C. The tape remainsimmersed in the hot water for a period of 2 seconds, immediatelyfollowing which the heated tape is forwarded through a first set of niprollers and then through a second set of nip rollers, with the distancebetween the first and second sets of nip rollers being about 6 feet.Between the first and second sets of nip rollers, the tape is subjectedto a solid state biaxial orientation. Orientation is produced byinflating the tape with a trapped bubble of air between the first andsecond sets of nip rollers. Additional orientation is provided byrunning the first set of nip rollers at a surface speed of 15 meters perminute, and the second set of nip rollers at a surface speed of 42meters per minute. The result is 2.8× orientation in the transversedirection and 2.8× orientation in the machine direction, for a totalbiaxial orientation of 7.8.

Example 70

The retortable film of Example 70 was prepared in a manner similar tothe preparation of the film of Example 69, described above. The film ofExample 70 also has a total of 7 layers, in the following order, withthe thickness of each layer of the tape (i.e., prior to solid stateorientation) shown in mils being indicated below the layer identity andresin composition:

Layer Arrangement, Composition, and Thickness of Film of Example 70

Outer Sealant Core Core High High melt 90% Nylon 1 + 10% 90% Nylon 1 +10% melt point Tie crystallinity Barrier crystallinity Tie point polymerTie 1 interrupter Barrier 1 interrupter Tie 1 polymer 1.5 mils 1 mil3.25 mils 1 mil 3.25 mils 1 mil 1.5 mils

The identity of the various resins in the film of Example 70 is the sameas in the table above in Example 69. The only additional resin, i.e.,the crystallinity interrupter, comprises at least one member selectedfrom the group consisting of: polyamide 6/12, polyamide 6/69, polyamide6I/6T, polyamide MXD6, polyamide MXDI, polyamide 66/610, amorphouspolyamide, polyether block amide copolymer, polyester (includingpolyethylene terephthalate/glycol), EVOH, polystyrene, polyolefin (e.g.,polybutene, long chain branched homogeneous ethylene/alpha-olefincopolymer, and linear low density polyethylene), and ionomer resin. Thecrystallinity interrupter is blended with the Nylon 1. Thesemi-crystalline polyamide is the primary component present in the blendwith the crystallilnity interrupter. The primary component makes up from60 to 99 weight percent of the blend and the secondary component makingup from 1 to 40 weight percent of the blend. Any heat-shrinkable,retortable film of the invention can comprise a blend of thesemi-crystalline polyamide with a crystallinity interrupter as set forthabove.

The annular die, air shoe, cooling air, water ring, cooling water, hotbath, immersion time, air ring, etc., and conditions, are all carriedout as set forth in Example 1, above.

Example 71

The retortable film of Example 71 is prepared in a manner similar to thepreparation of the film of Example 69, described above. However, thefilm of Example 71 is prepared by an extrusion coating process asillustrated in FIG. 5, described above. As shown in the table below, thefilm of Example 71 has a total of 8 layers, with the first 4 layersbeing coextruded from an annular die as a substrate, and the fifththrough eighth layers being extrusion-coated onto the substrate, theselast four layers being referred to as the coating layers. Thesemi-crystalline nylon is present in one of the substrate layers. As inExample 69 and Example 70, the extruded substrate portion of the film israpidly quenched upon emerging from the die. The rapid quench isaccomplished primarily by placing the water ring close to the die sothat a cascade of cool water contacts the annular extrudate immediatelyupon emergence of the extrudate from the die. While the various layersof the substrate may be irradiated, the coating layers are notirradiated. The coating layers provide the film with a high barrier toatmospheric oxygen (and other materials), add abuse resistance, andenhance the subsequent processability (i.e., orientability) of themultilayer extrudate.

Layer Arrangement, Composition, and Thickness of Film of Example 71

substrate coating Sealant Outer High melt substrate substrate Substratecoating coating coating High melt point Tie Core Tie Barrier Tie Corepoint polymer Tie 2 Nylon 1 Tie 2 Barrier 1 Tie 3 Bulk 1 polymer 3 mils1 mil 12 mils 1 mil 2 mils 1 mil 2 mils 1 milThe annular die used in the process has a diameter of 5 inches, and theair shoe has a diameter of 4.25 inches and a length of 13 inches. Thediameter of the coating die is 3.5 inches. Otherwise, the process usedto produce the film of Example 3 is as described in Example 1, above,including the cooling air, water ring, cooling water, hot bath,immersion time, and annealing apparatus and conditions. The identity ofthe various resins in the film of Example 71 are as follows:

Resin code Resin Identity High Melting MDPE, HDPE, PEC, PA copolymer, PPhomopolymer Point Polymer Tie 2 Anhydride grafted LLDPE, MDPE, HDPE, PP,EVA, EMA, PEC Tie 3 EVA, EMA Nylon 1 Semi-crystalline Nylon, AmorphousNylon Interrupter 1 polyamide 6/69, polyamide 6I/6T, polyamide MXD6,polyamide MXDI, polyamide 66/610, amorphous polyamide, polyether blockamide copolymer, polyester (including polyethyleneterephthalate/glycol), EVOH, polystyrene, polyolefin (e.g., polybutene,long chain branched homogeneous ethylene/alpha- olefin copolymer, andlinear low density polyethylene), and ionomer resin. Interrupter 1polyamide 6/69, polyamide 6I/6T, polyamide MXD6, polyamide MXDI,polyamide 66/610, amorphous polyamide, polyether block amide copolymer,polyester (including polyethylene terephthalate/glycol), EVOH,polystyrene, polyolefin (e.g., polybutene, long chain branchedhomogeneous ethylene/alpha- olefin copolymer, and linear low densitypolyethylene), and ionomer resin. Bulk 1 Polyolefin Barrier 1 EVOH,Retortable EVOH, Amorphous Nylon, MXD6, MXD6/MXDI, and nanocompositebarrier materialsThe resulting extrusion-coated tape is wound up onto a reel, transportedto a location for solid state orientation, and then unwound andbiaxially oriented in substantially the same manner described in Example69. The resulting retortable, heat-shrinkable multilayer film is thenannealed substantially as described in Example 69.

Example 72

The retortable film of Example 72 is prepared using an extrusion-coatingprocess as described in Example 71, above. As shown in the table below,the film of Example 72 also has a total of 8 layers, with the first 4layers being the substrate layers, and the fifth through eighth layersbeing the coating layers.

Layer Arrangement, Composition, and Thickness of Film of Example 72

substrate coating Sealant Substrate Outer High melt substrate CoreSubstrate coating coating coating High melt point Tie Nylon 1 +crystalline Tie Barrier Tie Core point polymer Tie 2 interrupter Tie 2Barrier 1 Tie 3 Bulk 1 polymer 3 mils 1 mil 12 mils 1 mil 2 mils 1 mil 2mils 1 milThe annular die, air shoe, cooling air, water ring, cooling water, hotbath, immersion time, and annealing apparatus and conditions were allcarried out asset forth in Example 71, above. The identity of thevarious resins in the film of Example 72 is the same as in the tableabove in Example 71. The only additional resin, i.e., thesemi-crystalline interrupter, is the same as the semi-crystallineinterrupter in Example 70, above. Otherwise, the process used to producethe film of Example 72 is as described in Example 71, above.

Example 73

A coextruded multilayer heat-shrinkable retortable film was producedutilizing the apparatus and process set forth in FIGS. 1, 2, and 3,described above. The multilayer film had a total of 7 layers, in thefollowing order, with the thickness of each layer of the tape (i.e.,prior to solid state orientation) indicated below the layer identity andresin composition identification:

Layer Arrangement, Composition, and Thickness of Film of Example 73

Sealant Tie Core Barrier Core Tie Outer MDPE 1 Tie 4 Nylon 2 EVOH 1Nylon 2 Tie 4 MDPE 1 1.5 mils 1 mil 3.25 mils 1 mil 3.25 mils 1 mil 1.5milsThe identity of the various resins in the film of Example 73 was asfollows:

Resin code Resin Identity MDPE1 Dow Dowlex ® 2037 0.935 D Tie 4 EquistarPlexar ® PX3227 Nylon 2 BASF Ultramid ® B40 EVOH 1 EVAL LC-E105AThe 7-layer extrudate (i.e., tape) was coextruded (i.e., downward cast)from an annular die (diameter of 5 inches) over an air shoe thatprovided the emerging melt stream with the needed support to minimizegauge band variation in the resulting tape. The air shoe had an outsidediameter of 4.25 inches and a length of 13 inches, and emitted cool air(15.6° C.) through 0.030 inch diameter holes spaced over the outercylindrical surface of the air shoe, the holes being spaced apart by adistance of 0.5625 inch, with the holes being arranged so that each holeinside the matrix of holes were surrounded by 6 holes. The airflowthrough the holes supported the film (so that it did not collapse due toimpingement of a flow of cool water thereon, as described below) andcooled the film from the inside out, i.e., to assist in “freezing” thenylon quickly to minimize crystallization of the nylon. The pressurebetween the air shoe and the inside surface of the tape was slightlyabove atmospheric pressure (i.e., about 1.03 atmosphere). The cool airwas pumped into the hollow air shoe and out the small holes terminatingthe passageways leading from the internal chamber within the air shoe tothe outer surface thereof. The cool air flowed downward in the small gap(about 0.005 inch) between the tape and the outer surface of the airshoe, the cool air then passing into and upwardly through the centrallylocated pipe, after which the air passed out of the upper end of thepipe and into the environment.

Although the air shoe assisted in freezing the polyamide to minimizecrystallization thereof, most of the heat in the extrudate emerging fromthe die was removed by a stream of cool water emitted from a water ringpositioned approximately 2 inches downstream of the annular die. Thewater ring emitted a stream of cool water (about 7.2° C.) against theouter surface of the extrudate to produce sudden freezing (i.e.,quenching) of the polymers in the various film layers. The suddenquenching was employed particularly for the purpose of quickly quenching(and thereby minimize the crystallization) of the semi-crystallinepolyamide in each of the two core layers identified in the table above.The water ring was sized so that its inside surface was from 1-2 inchesfrom the extrudate. The water ring was positioned so that the annularstream of cool water it emitted contacted the extrudate about 2 inchesdownstream of the point at which the extrudate emerged from the annulardie. The water was emitted from the water ring as a stream in aninitially horizontal direction, with the stream arcing downward slightlybefore making contact with the extrudate. This very rapid quenchingprocess, coupled with a minimization of dwell time in a hot water bathbefore orientation and the relatively low temperature of the hot bath(described below), the positioning and emission of the cool air from anair ring (also described below), all assist in orienting the extrudatein a manner resulting in the heat-shrinkability, and other properties,set forth below.

Beneath the die, the quenched tape was collapsed into lay-flatconfiguration and wound up onto a reel. The reel of quenched tape inlay-flat configuration was then transported to a location forsolid-state orientation. The tape was then unwound and forwarded to abath containing hot water at a temperature of 71° C. The tape wascontinuously forwarded through the bath with a residence time of about 2seconds of immersion in the hot water, following which the resultingheated tape was immediately forwarded through a first set of nip rollersfollowed by a second set of nip rollers, with the distance between thefirst and second sets of nip rollers being about 6 feet. The tape wasbiaxially-oriented between the upper and lower sets of nip rollers bypassing the tape around a trapped bubble of air. Biaxial orientation wasproduced by both (a) inflating the tape with the trapped bubble of airbetween the sets of nip rollers, and (b) running the first set of niprollers at a surface speed of 15 meters per minute, and running thesecond set of nip rollers at a surface speed of 42 meters per minute.The result was about 2.8× orientation in the transverse direction andabout 2.8× orientation in the machine direction, for a total biaxialorientation of about 7.8×. The resulting retortable, annular,heat-shrinkable, coextruded film was not annealed.

The resulting retortable, heat-shrinkable, coextruded film exhibited ahigh total free shrink at 185° F., a high abrasion resistance, a highpuncture strength, and was able to withstand retort conditions of 250°F. for 90 minutes. At this condition a total shrink of 1% wasexperienced. The table below provides the gauge and free shrink of theretortable, heat-shrinkable film of Example 73.

Film of Film Gauge % free shrink at Example No. (mils) 185° F. (L + T)70 2.1 26 + 25

Examples 74-78

Examples 74-78 were five additional heat-shrinkable, retortable filmsproduced utilizing the apparatus and process set forth in FIGS. 1, 2,and 3, described above, i.e., as set forth in Example 70, above. Each ofthe films of Examples 74-78 had a total of 7 layers, in the followingorder, with the percent thickness of each layer of the tape and filmbeing indicated at the bottom of the layer composition description.

Layer Arrangement, Composition, and Thickness of Films of Examples 74-78

Tie Tie Outer layer layer Bulk layer Barrier layer Bulk layer layerOuter layer Example MDPE 1 Tie 4 90% Amorphous 90% Tie 4 MDPE 1 71 Nylon1 Nylon Nylon 1 10% 10% Amorphous Amorphous Nylon Nylon % of 12 8 26 826 8 12 film Example 65% Tie 4 90% Amorphous 90% Tie 4 65% 72 MDPE Nylon1 Nylon Nylon 1 MDPE 30% HDPE 10% 10% 30% HDPE 5% Slip 1 AmorphousAmorphous 5% slip Nylon Nylon % of 12 8 26 8 26 8 12 film Example LLDPE1 Tie 4 90% Amorphous 90% Tie 4 LLDPE 1 73 Nylon 1 Nylon Nylon 1 10% 10%Amorphous Amorphous Nylon Nylon % of 12 8 26 8 26 8 12 film Example P-ECop Tie 4 90% Amorphous 90% Tie 4 P-E Cop 74 Nylon 1 Nylon Nylon 1 10%10% Amorphous Amorphous Nylon Nylon % of 12 8 26 8 26 8 12 film Example50% P-E Tie 4 90% Amorphous 90% Tie 4 50% P-E 75 Copolymer Nylon 1 NylonNylon 1 Copolymer 44% homo 10% 10% 44% homo VLDPE Amorphous AmorphousVLDPE 6% slip & Nylon Nylon 6% slip & antiblock antiblock % of 012 8 268 26 8 12 film

The identity of the various resins in the films of Examples 74-78 areset forth in the table below. Resin codes set forth in the table above,but not identified in the resin identity table below, are as set forthin the resin identity table in Example 73.

Resin code Resin Identity Amorphous Nylon Selar ® PA 3426 amorphousnylon 1.19 g/cc (DuPont) HDPE Fortiflex ® T60-500-119 high densitypolyethylene; 0.961 g/cc, 6.0 g/10 min (Ineos) Slip 1 10850 antiblockand slip in LLDPE; 0.95 g/cc; 1.8 g/10 min (Ampacet) LLDPE 1 Dowlex ®2045.03 linear low density polyethylene; 0.92 g/cc, 1.1 g/ 10 min (Dow)P-E Copolymer ED 01-03 propylene-ethylene copolymer; 0.90 g/cc; 8 g/10min; 134° C. mp (Total Petrochemicals) Homo VLDPE Single site catalyzedExact ® 3128 ethylene/butene copolymer; 0.900 g/cc; 1.3 g/10 min(ExxonMobil) Slip & Antiblock 102804 antiblock and slip in HDPE; 1.02g/cc, 7.1 g/10 min (Ampacet)

The table below provides the thickness and total free shrink for theretortable, heat-shrinkable film of Examples 74-78:

Film % free shrink at Film of Gauge 185° F. Example No. (mils) (L + T)71 2.9 27 + 37 72 2.7 28 + 32 73 3.4 35 + 43 74 2.8 20 + 27 75 2.9 20 +24

Example 79

An extrusion-coated, heat-shrinkable retortable film was producedutilizing the apparatus and process set forth in FIG. 5, describedabove. The film had a total of 8 layers, in the following order, withthe thickness of each layer of the tape (i.e., prior to solid stateorientation) indicated below the layer identity and resin compositionidentification:

Layer Arrangement, Composition, and Thickness of Film of Example 79

substrate substrate substrate substrate coating coating coating coatingSealant Tie Core Tie Barrier Tie Core Outer MDPE 2 Tie 5 Nylon 2 Tie 5PVDC Tie 6 Bulk 1 MDPE 2 3 mils 1 mil 12 mils 1 mil 2 mil 1 mil 2 mils 1mil

The identity of the various resins in the film of Example 79 was asfollows:

Resin code Resin Identity MDPE 2 Dow Dowlex ® 2035 0.937 D Tie 5Equistar Plexar ® PX1007 Nylon 2 BASF Ultramid ® B40 Tie 6 ExxonMobilEscorene ® LD761.36 Bulk 1 Exxon Mobile Exceed ® 1012 PVDC Dow Saran ®806The four-layer substrate extrudate was extruded (i.e., downward cast)from an annular die (diameter of 5 inches) over an air shoe thatprovided the emerging melt stream with the needed support to minimizegauge band variation in the resulting tape. The air shoe had an outsidediameter of 4.25 inches and a length of 13 inches, and emitted cool air(15.6° C.) through 0.030 inch diameter holes spaced over the outercylindrical surface of the air shoe, the holes being spaced apart by adistance of 0.563 inch, with the holes being arranged so that each holeinside the matrix of holes were surrounded by 6 holes. The airflowthrough the holes supported the film (so that it did not collapse due toimpingement of a flow of cool water thereon, as described below) andcooled the film from the inside out, i.e., to assist in “freezing” thesemi-crystalline polyamide quickly to minimize crystallization of thesemi-crystalline polyamide. The pressure between the air shoe and theinside surface of the tape was slightly above atmospheric pressure(i.e., about 1.03 atmosphere). The cool air was pumped into the hollowair shoe and out the small holes terminating the passageways leadingfrom the internal chamber within the air shoe to the outer surfacethereof. The cool air flowed downward in the small gap (about 0.005inch) between the tape and the outer surface of the air shoe, the coolair then passing into and upwardly through the centrally-located pipe,after which the air passed out of the upper end of the pipe and into theenvironment.

Although the air shoe assisted in freezing the semi-crystallinepolyamide to minimize crystallization thereof, most of the heat in theextrudate emerging from the die was removed by a stream of cool wateremitted from a water ring positioned approximately 2 inches downstreamof the annular die. The water ring emitted a stream of cool water (about7.2° C.) against the outer surface of the extrudate to produce suddenfreezing (i.e., quenching) of the polymers in the various film layers.The sudden quenching was employed particularly for the purpose ofquickly quenching (and thereby minimize the crystallization) thesemi-crystalline polyamide in the core layer of the substrate, i.e., thecore layer identified in the table above. The cool water contacted theextrudate at a distance of approximately 2 inches downstream of theannular die. This very rapid quenching process, coupled with aminimization of dwell time in a downstream hot water bath (describedbelow), the positioning and emission of the cool air from an air ring(also described below), all assist in orienting the extrudate in amanner resulting in the heat-shrinkablility, and other properties, setforth below.

Beneath the die, the quenched substrate tape was collapsed into lay-flatconfiguration. The resulting irradiated annular tape, in lay-flatconfiguration, was directed through two sets of nip rollers having atrapped bubble of air therebetween, with the annular tape beingreconfigured from lay-flat configuration to round configuration by beingdirected around the trapped bubble of air. See FIG. 5. The resultinground annular substrate was then directed through a vacuum chamber,immediately following which the round annular substrate was passedthrough an extrusion-coating die, which extruded a 4-layer coatingstream onto and around the outside surface of the reconfigured annularsubstrate. The resulting 8-layer extrusion-coated tape was thenforwarded through and cooled by an air ring, and then reconfigured backto lay-flat configuration by being forwarded through the second of thepairs of nip rollers, with the extrusion-coated tape then being wound upon a roll. Again, see FIG. 5.

The substrate tape was not significantly drawn (either longitudinally ortransversely) as it was directed around the trapped bubble of airassociated with the extrusion coating apparatus. The surface speed ofthe nip rollers downstream of the trapped bubble was about the same asthe surface speed of the nip rollers upstream of the trapped bubble.Furthermore, the annular substrate tape was inflated only enough toprovide a substantially circular tubing without significant transverseorientation, i.e., without transverse stretching. The extrusion coatingwas carried out in a manner in accordance with U.S. Pat. No. 4,278,738,to BRAX et. al., referred to above.

The roll of 8-layer, annular, extrusion-coated tape was transported to alocation for solid-state orientation. The tape was then unwound andforwarded to a bath containing hot water at a temperature of 71° C. Thetape was continuously forwarded through the bath with a residence timeof about 2 seconds of immersion in the hot water, following which theresulting heated tape was immediately forwarded through a first set ofnip rollers followed by a second set of nip rollers, with the distancebetween the first and second sets of nip rollers being about 6 feet. Thetape was biaxially-oriented between the upper and lower sets of niprollers by passing the tape around a trapped bubble of air. Biaxialorientation was produced by both (a) inflating the tape with the trappedbubble of air between the sets of nip rollers, and (b) running the firstset of nip rollers at a surface speed of 15 meters per minute, andrunning the second set of nip rollers at a surface speed of 38 metersper minute. The result was about 2.5× orientation in the transversedirection and about 2.5× orientation in the machine direction, for atotal biaxial orientation of about 6.25×. The resulting retortable,heat-shrinkable, extrusion-coated film exhibited a high total freeshrink at 185° F., a high abrasion resistance, and a high puncturestrength, and was able to withstand retort conditions of 250° F. for 90minutes.

1. A process for making a heat-shrinkable annular film, comprising: (A)extruding an annular extrudate downward from an annular die, theextrudate comprising at least one semi-crystalline polyamide, thesemi-crystalline polyamide comprising at least one member selected fromthe group consisting of: (i) polyamide 6, (ii) polyamide 66, (iii)polyamide 6/66, and (iv) polyamide 6/12, and with the semi-crystallinepolyamide making up at least 5 volume percent of the annular extrudate,based on total extrudate volume; (B) quenching the annular extrudate byapplying a quenching liquid to the annular extrudate, with the quenchingliquid absorbing heat from the annular extrudate as at least 50% of thequenching liquid cascades down the annular extrudate for a distance ofat least 2 inches, the quenching liquid making initial contact with theannular extrudate at a distance of from 0.1 to 8 inches downstream of apoint at which the annular extrudate emerges from the annular die; (C)reheating the extrudate to an orientation temperature of from 130° F. to210° F., resulting in a reheated annular extrudate; (D) orienting thereheated annular extrudate while the reheated annular extrudate is inthe solid state, the orientation being carried out with a totalorientation factor of at least 2, so that an oriented, heat-shrinkablefilm is produced, the oriented film having a total free shrink at 185°F. of at least 10 percent.
 2. The process according to claim 1, whereinthe quenching liquid passes through a central passageway through theannular die and into to an interior volume within the annular extrudate,the interior volume being between a point at which the annular extrudateemerges from the annular die and a point at which the annular extrudateconverges into lay-flat configuration, the quenching liquid beingapplied to an inside surface of the annular extrudate, the quenchingliquid cascading downward into a collection pool above the point atwhich the annular extrudate converges into lay-flat configuration, withthe quenching liquid being drawn out of the collection pool and upthrough a discharge conduit passing through the central passagewaythrough the annular die, so that the extrudate is quenched by thequenching liquid cascading down the interior surface of the annularextrudate.
 3. The process according to claim 1, further comprisingquenching the extrudate by contacting an outside surface of the annularextrudate with the quenching liquid and supporting the annular extrudatewith a means for supporting, the means for supporting being inside theannular extrudate, the supporting of the extrudate beginning at adistance of from 0 to 8 inches downstream the point at which theextrudate emerges from the annular die.
 4. The process according toclaim 3, wherein the means for supporting the extrudate comprisescontacting an inside surface of the annular extrudate with a secondquenching liquid provided to a second means for and supporting theannular extrudate with a means for supporting located inside the annularextrudate, the supporting of the extrudate beginning at a distance offrom 0 to 8 inches downstream the point at which the extrudate emergesfrom the annular die.
 5. The process according to claim 3, wherein themeans for supporting is provided by supplying a gas to an interiorvolume within the annular extrudate, the interior volume being between apoint at which the annular extrudate emerges from the annular die and apoint at which the annular extrudate converges into lay-flatconfiguration, the gas being provided so that the interior volume has apressure above ambient pressure.
 6. The process according to claim 5,wherein the means for supporting further comprises an air shoepositioned in the interior volume of the annular extrudate, the air shoeemitting air therefrom to provide a supportive air cushion between theextrudate and the air shoe, the air shoe providing the supportive aircushion between the extrudate and the air shoe at a distance beginningfrom 0 to 8 inches downstream of the annular die.
 7. The processaccording to claim 6, wherein the air shoe emits air having atemperature of from −10° C. to 25° C.
 8. The process according to claim6, wherein the air shoe emits air having a temperature of from 0° C. to25° C.
 9. The process according to claim 6, wherein the air shoe emitsair having a temperature of from 5° C. to 10° C.
 10. The processaccording to claim 6, wherein the air shoe has a length of from about 4inches to about 50 inches, and a diameter of from about 1 inch to about50 inches, the air shoe having a plurality of airflow holes therein,each hole having a diameter of from about 0.01 to about 0.25 inch, andthe holes in the air shoe are within a distance of from about 2millimeters to about 40 millimeters of one another.
 11. The processaccording to claim 6, wherein air under a pressure of from about 1 toabout 100 pounds per square inch is supplied to the air shoe.
 12. Theprocess according to claim 6, wherein a ratio of an inside diameter ofthe annular die gap to the outside diameter of the air shoe is fromabout 1:1.1 to about 1:0.5.
 13. The process according to claim 1,wherein at least 70 percent of the quenching liquid cascades down theextrudate for a distance of at least 3 inches, the quenching liquidmaking initial contact with the extrudate at a distance of from 0.1 to 6inches downstream of the annular die.
 14. The process according to claim1, wherein the quenching liquid is applied to an outside surface of theannular extrudate, and at least 80 percent of the quenching liquidcascades down the extrudate for a distance of at least 4 inches, thequenching liquid making initial contact with the extrudate at a distanceof from 0.1 to 5 inches downstream of the annular die.
 15. The processaccording to claim 1, wherein the quenching liquid is applied to anoutside surface of the annular extrudate, and at least 90 percent of thequenching liquid cascades down the extrudate for a distance of at least5 inches, the quenching liquid making initial contact with the extrudateat a distance of from 0.1 to 4 inches downstream of the annular die. 16.The process according to claim 1, wherein the quenching liquid isapplied to an outside surface of the annular extrudate, and at least 99percent of the quenching liquid cascades down the extrudate for adistance of at least 8 inches, the quenching liquid making initialcontact with the extrudate at a distance of from 0.3 to 3 inchesdownstream of the annular die.
 17. The process according to claim 16,wherein the quenching liquid making initial contact with the annularextrudate at a distance of from 1 to 3 inches downstream of the annulardie.
 18. The process according to claim 1, wherein the quenching liquidmakes initial contact with the outside surface of the annual extrudateat a distance of from 1.5 to 3 inches downstream of the annular die. 19.The process according to claim 1, wherein the quenching liquid compriseswater and the quenching liquid is emitted from a water ring and thequenching liquid is at a temperature of from 0° C. to 25° C. as itemerges from the water ring.
 20. The process according to claim 19,wherein the quenching liquid is emitted from the water ring at atemperature of from 5° C. to 16° C.
 21. The process according to claim1, wherein the quenching liquid is applied to the annular extrudate froma plurality of water rings, with a stream of water being applied to theoutside surface of the extrudate from each water ring.
 22. The processaccording to claim 1, wherein the semi-crystalline polyamide makes up atleast 30 volume percent of the film, based on total film volume.
 23. Theprocess according to claim 1, wherein the semi-crystalline polyamidemakes up at least 35 volume percent of the annular extrudate, based ontotal extrudate volume, and the orientation is carried out with a totalorientation factor of at least 5, and the oriented film exhibits a totalfree shrink at 185° F. of at least 30 percent.
 24. The process accordingto claim 1, wherein the semi-crystalline polyamide makes up at least 40weight percent of the annular extrudate, based on total extrudateweight, and the orientation is carried out with a total orientationfactor of at least 6, and the oriented film exhibits a total free shrinkat 185° F. of at least 40 percent.
 25. The process according to claim 1,wherein the semi-crystalline polyamide makes up at least 50 weightpercent of the annular extrudate, based on total extrudate weight, andthe orientation is carried out with a total orientation factor of atleast 7, and the oriented film exhibits a total free shrink at 185° F.of at least 50 percent.
 26. The process according to claim 1, whereinthe semi-crystalline polyamide makes up at least 60 weight percent ofthe annular extrudate, based on total extrudate weight, and theorientation is carried out with a total orientation factor of at least8, and the oriented film exhibits a total free shrink at 185° F. of atleast 55 percent.
 27. The process according to claim 1, wherein thereheating is carried out by immersing the extrudate in a hot bath havinga temperature of from 130° F. to 180° F., with the extrudate beingimmersed for a period of from 1 to 40 seconds.
 28. The process accordingto claim 27, wherein the reheating is carried out by immersing theextrudate in a hot bath at a temperature of from 145° F. to 175° F.,with the extrudate being immersed for a period of from 2 to 10 seconds.29. The process according to claim 28, wherein the reheating is carriedout by immersing the extrudate in a hot bath at a temperature of from150° F. to 170° F., with the extrudate being immersed for a period offrom 3 to 7 seconds.
 30. The process according to claim 29, wherein thehot bath contains hot water, and the annular extrudate is reheated byimmersion in the hot water.
 31. The process according to claim 1,wherein the semi-crystalline polyamide in the second layer is a primarycomponent present in a blend with a secondary component, with theprimary component making up from 20 to 99 weight percent of the blend,and the secondary component making up from 1 to 80 weight percent of theblend, and the secondary component comprises at least one memberselected from the group consisting of polyamide 6/69, polyamide MXD6,polyamide MXDI, polyamide 66/610, amorphous polyamide, polyether blockamide copolymer, polyester, EVOH, polystyrene, polyolefin, and ionomerresin.
 32. The process according to claim 1, wherein the annularextrudate has a total thickness of from about 5 mils to about 70 mils.33. The process according to claim 1, wherein the heat-shrinkable filmhas a total thickness of from about 1 to 5 mils.
 34. The processaccording to claim 1, wherein a biaxial orientation is carried out bypassing the reheated extrudate over a trapped bubble of air whilesimultaneously drawing the reheated extrudate in its a longitudinaldirection.
 35. The process according to claim 1, further comprisingannealing the heat-shrinkable multilayer film.
 36. The process accordingto claim 1, further comprising irradiating the annular extrudate. 37.The process according to claim 1, further comprising extrusion-coatingone or more additional layers onto the annular extrudate.
 38. Theprocess according to claim 37, wherein at least two additional layersare extrusion coated onto the annular extrudate, and at least one of theadditional layers comprises polyvinylidene chloride.
 39. The processaccording to claim 1, wherein the annular extrudate is multilayer andcomprises: (A) a first layer, the first layer being an outer film layerwhich serves as a heat seal layer, the first layer comprising at leastone member selected from the group consisting of (i) a polyolefin havinga density of from 0.88 g/cm³ to 0.917 g/cm³, and (ii) ionomer resin; (B)a second layer comprising at least one semi-crystalline polyamideselected from the group consisting of polyamide 6, polyamide 66,polyamide 6/66, and polyamide 6/12.
 40. The process according to claim39, wherein the multilayer extrudate further comprises: (A) a thirdlayer that serves as a barrier layer, the third layer comprising atleast one member selected from the group consisting of hydrolyzedethylene/vinyl acetate copolymer, polyvinylidene chloride, amorphouspolyamide, polyamide MXD6, polyester, and polyacrylonitrile; and (B) afourth layer that serves as a tie layer, the fourth layer being betweenthe first layer and the third layer.
 41. The process according to claim40, wherein the first layer is a first outer layer, the fourth layer isa first tie layer, and the second layer is directly adhered to the thirdlayer, and the multilayer film further comprises a fifth layer that is asecond outer layer a sixth layer that serves as a second tie layer, thesixth layer being between the fifth layer and third layer.
 42. Theprocess according to claim 41, wherein the extrudate has the followinglayer arrangement: seal/first tie/polyamide/second tie/barrier/third tiesecond outer wherein the seal layer is the first layer, the first tielayer is the fourth layer, the polyamide layer is the second layer, thebarrier layer is the third layer, the second tie layer is the sixthlayer, and the outer layer is the fifth layer.
 43. The process accordingto claim 41, wherein the polyamide layer is a first polyamide layer, andthe film further comprises a seventh layer that is a second polyamidelayer, and the film has the following layer arrangement: seal/firsttie/first polyamide/barrier/second polyamide/second tie/second outer.44. The process according to claim 41, wherein the second outer layercomprises at least one member selected from the group consisting ofethylene/alpha-olefin copolymer, olefin homopolymer, polyamide,polyester, ethylene/unsaturated ester copolymer, and ionomer resin. 45.The process according to claim 1, wherein the annular extrudatecomprises polyamide in an amount of at least 85 volume percent, based ontotal film volume.
 46. The process according to claim 45, wherein theannular extrudate comprises polyamide in an amount of at least 98percent, based on total film volume.
 47. The process according to claim45, wherein the annular extrudate comprises polyamide in an amount ofsubstantially 100 percent, based on total film volume.
 48. The processaccording to claim 45, wherein the annular extrudate comprises: (A) afirst layer, the first layer being an outer film layer which serves as aheat seal layer, the first layer comprising at least one member selectedfrom the group consisting of: (i) a semi-crystalline polyamide having amelting point of up to 215° C. and (ii) a blend of a semi-crystallinepolyamide having a melting point of above 215° C. with (a) amorphouspolyamide and/or (b) or semi-crystalline polyamide having a meltingpoint of up to 215° C.; and (B) a second layer comprising at least onesemi-crystalline polyamide having a melt point above 215° C.
 49. Theprocess according to claim 48, wherein the a second layer comprises ablend of the semi-crystalline polyamide having a melt point above 215°C. with at least one member selected from the group consisting ofpolyamide 6/12 having a melt point below 215° C., polyamide 6/69,polyamide MXD6, polyamide 66/610, and amorphous polyamide.
 50. Theprocess according to claim 1, wherein the annular extrudate is notirradiated before it is oriented.